Project: Anti-roll-bar for the front axis. Discussion!
- Thread starter A2-D2
- Start date
Mustang-owner
Donor
Manuel,
My H&R Kit arrived this morning too.
Thank you very much
Jeff
My H&R Kit arrived this morning too.
Thank you very much
Jeff
A2 Cars
Member
Today we received a bulk order of H&R ARB kits - thank you to the members that notified us of their purchase. This has been confirmed with Manuel and we will communicate with you to make arrangements to fit the kits.
Other members that have also received their H&R ARB's directly and require a fitting service, drop us a call, PM or email.
blue skies
tony
Other members that have also received their H&R ARB's directly and require a fitting service, drop us a call, PM or email.
blue skies
tony
Steven Garrity
A2OC Donor
Hi,
Manuel,
My H&R Kit arrived this morning too.
Thank you very much
Steven Garrity
Manuel,
My H&R Kit arrived this morning too.
Thank you very much
Steven Garrity
Captain059
A2OC Donor
Hi guys and girls
I have collected my kit from my neighbour today. It arrived on Tuesday but I was absent all week.
Thanks to Manuel for this great opportunity.
I hope to get it installed very soon.
I have collected my kit from my neighbour today. It arrived on Tuesday but I was absent all week.
Thanks to Manuel for this great opportunity.
I hope to get it installed very soon.
bretti_kivi
Member
so my front one got installed today.
Wow. I run B8s, Eibachs, and at the moment am on 185/60R15 winter tyres. The limiting factor on *any* corner is now tyre grip. I can push them in any corner I want at least 10 km/h faster than yesterday and it'll be those that let go way before it even feels remarkably fast, because there's pretty much *zero* roll now. I have no idea how this is going to be in the summer, but wow, this is going to be good in the cold.
If I move my hand from the elbow at the 12 o'clock position on the wheel - at 50km/h (30mph) - that translates *immediately* to movement on the road. No hesitation, zero squidge, just gokart. And that's on 60 profile winter tyres! It's no more squirrely than before and not much stiffer at lower speeds. The B8s turn into treacle at around zero, that's fair enough, but this is a serious improvement. The Fi will feel like a bottle of fairy liquid after my car.
I don't see comfort impinged much, but other incident deserves a write-up: I was out on Tuesday or so as it was cold. Around -3 or so, it was extremely slippery outside, so at a convenient roundabout and carpark, I did a couple of tests. A left-right flick on the roundabout meant the back end came around the way it should, and the higher-speed stuff in the carpark was just sliding predictably. Monster was with and she complained about having to hold on to the door, while laughing; the G-Forces can be there. She's too small to be held properly by the sports seats so gets thrown around quite a lot....
One other thing I did do which may have helped: the dogbone is also replaced with a superpro item. It was due for replacement, but the new one does transmit a few too many vibrations at tickover. But the immediacy is awesome.
- Bret
Wow. I run B8s, Eibachs, and at the moment am on 185/60R15 winter tyres. The limiting factor on *any* corner is now tyre grip. I can push them in any corner I want at least 10 km/h faster than yesterday and it'll be those that let go way before it even feels remarkably fast, because there's pretty much *zero* roll now. I have no idea how this is going to be in the summer, but wow, this is going to be good in the cold.
If I move my hand from the elbow at the 12 o'clock position on the wheel - at 50km/h (30mph) - that translates *immediately* to movement on the road. No hesitation, zero squidge, just gokart. And that's on 60 profile winter tyres! It's no more squirrely than before and not much stiffer at lower speeds. The B8s turn into treacle at around zero, that's fair enough, but this is a serious improvement. The Fi will feel like a bottle of fairy liquid after my car.
I don't see comfort impinged much, but other incident deserves a write-up: I was out on Tuesday or so as it was cold. Around -3 or so, it was extremely slippery outside, so at a convenient roundabout and carpark, I did a couple of tests. A left-right flick on the roundabout meant the back end came around the way it should, and the higher-speed stuff in the carpark was just sliding predictably. Monster was with and she complained about having to hold on to the door, while laughing; the G-Forces can be there. She's too small to be held properly by the sports seats so gets thrown around quite a lot....
One other thing I did do which may have helped: the dogbone is also replaced with a superpro item. It was due for replacement, but the new one does transmit a few too many vibrations at tickover. But the immediacy is awesome.
- Bret
timmus
A2OC Donor
Thanks for the write-up, Bret. Personally, my greatest concern is the effect upon comfort. I shall not be fitting my kit until I'm convinced that comfort isn't overly compromised. Further feedback in due course on this aspect in particular would be much appreciated.
Cheers,
Tom
Cheers,
Tom
Birchall
Dick Chown Award 2016
Hi Tom,
This is not aimed at you or anyone else who already understands how an anti roll bar (ARB) works, it is just for those that perhaps don't know.
Essentially an ARB has ZERO affect on the spring stifness when the car is driving along in a straight line and both wheels are compressed or uncompressed equally (i.e. on normal roads (without pot holes!!).
In fact, in a straight line you wouldn't be able to tell if the car had an anti roll bar or not! t
The exception being when experiencing side-winds at speed on a motorway for example. Because the wind makes the car swerve a bit, the ARB does help a little to keep it on a straight line because the car is then NOT compressed equally on both sides..
What happens is that the ends of the ARB are attached to each suspension in a kind of elongated U shape and the mounts allow it to swivel up and down as the wheels compress when hitting a speed bump, for example. If both sides are compressed by the same amount , then it merely swivels upwards and does not play any part.
BUT, when one side of the suspenson is compressed and the other isn't, the ARB has to twist and so it acts like an additional spring
So an ARB really does give you the best of both worlds, stiffer spring rates when cornering with NO extra stiffness when driving straight ahead on even roads.
The stifness when cornering results in less roll (hence the name Anti ROLL bar)
This is VERY basic engineering but a GREAT aid to handling, whith few, if any, negatives.
The thicker the ARB, the stiffer the spring rate will be when cornering (again with zero impact when both wheels are equally compressed or equally uncompressed.
Manufacturers try to err towards comfort (they assume that most of their customers are NOT Lewis Hamilton) and so they use reasonably soft ARBs.
So an upgrade like this really can improve handling without any negative effect on normal "straight line" comfort.
In fact I once bought an A2 that had the standard front ARB removed altogether and it was almost impossible to tell the difference (mainly because I never corenered that hard on public roads).
I am not sure that a rear ARB on an A2 will transform the handling as much, because it is not independent suspension on the rear anyway, in fact the rear axle on an A2 can seriously be thought of as an ARB anyway, that is the way it has been designed, it can twist when corenering and increase the sprng rate.
Yes adding an ARB to the rear will, of course, stiffen the suspension when cornering, as any ARB would, but the difference is that the rear ARB on an A2 is the axle itself anyway, and so the difference will not be so quite so large.
But first-hand experience from many on here is that it makes a big difference and I certainly won't doubt first-hand experience above theory, any day.
As I say, this is just to help demistify the ARB and what it does, for those that didn't know.
Steve B
This is not aimed at you or anyone else who already understands how an anti roll bar (ARB) works, it is just for those that perhaps don't know.
Essentially an ARB has ZERO affect on the spring stifness when the car is driving along in a straight line and both wheels are compressed or uncompressed equally (i.e. on normal roads (without pot holes!!).
In fact, in a straight line you wouldn't be able to tell if the car had an anti roll bar or not! t
The exception being when experiencing side-winds at speed on a motorway for example. Because the wind makes the car swerve a bit, the ARB does help a little to keep it on a straight line because the car is then NOT compressed equally on both sides..
What happens is that the ends of the ARB are attached to each suspension in a kind of elongated U shape and the mounts allow it to swivel up and down as the wheels compress when hitting a speed bump, for example. If both sides are compressed by the same amount , then it merely swivels upwards and does not play any part.
BUT, when one side of the suspenson is compressed and the other isn't, the ARB has to twist and so it acts like an additional spring
So an ARB really does give you the best of both worlds, stiffer spring rates when cornering with NO extra stiffness when driving straight ahead on even roads.
The stifness when cornering results in less roll (hence the name Anti ROLL bar)
This is VERY basic engineering but a GREAT aid to handling, whith few, if any, negatives.
The thicker the ARB, the stiffer the spring rate will be when cornering (again with zero impact when both wheels are equally compressed or equally uncompressed.
Manufacturers try to err towards comfort (they assume that most of their customers are NOT Lewis Hamilton) and so they use reasonably soft ARBs.
So an upgrade like this really can improve handling without any negative effect on normal "straight line" comfort.
In fact I once bought an A2 that had the standard front ARB removed altogether and it was almost impossible to tell the difference (mainly because I never corenered that hard on public roads).
I am not sure that a rear ARB on an A2 will transform the handling as much, because it is not independent suspension on the rear anyway, in fact the rear axle on an A2 can seriously be thought of as an ARB anyway, that is the way it has been designed, it can twist when corenering and increase the sprng rate.
Yes adding an ARB to the rear will, of course, stiffen the suspension when cornering, as any ARB would, but the difference is that the rear ARB on an A2 is the axle itself anyway, and so the difference will not be so quite so large.
But first-hand experience from many on here is that it makes a big difference and I certainly won't doubt first-hand experience above theory, any day.
As I say, this is just to help demistify the ARB and what it does, for those that didn't know.
Steve B
bretti_kivi
Member
Hi,
I think this deserves a post of its own, because we end up looking at the term "comfort".
TL;DR version: in my eyes, suspension compliance is not important but very nice to have. Nod and squat are annoying rather than a problem. Roll is something I do not like, and neither do my passengers. So the ARBs provide a very nice solution to the issue of roll without compromising the other values of the suspension setup.
The rest of the post:
I'm living in a country where poor A- and B-Class roads are the ones I drive most frequently, so I need something that is stable at speed on suboptimal surfaces, allows me to drive gravel without compromising too much, and which corners nicely. The standard routes to the airport and the office are mainly motorway; to the northern office it's straight roads but much traffic and to the summer house it's three hours of poorly-asphalted curves with ludicrous quantities of bumps and hollows. To allow any confidence, the car needs to feel good and planted. The speed limits are generally low but not having to flick cruise off is a bonus.
The baseline has to be the original setup in an A2. The TDIs are slightly heavier over the front axle, and as a result have a slightly higher spring rate. This is mirrored with the FSI, whereas the 1.4 petrol has a lower spring rate. For any of the vehicles, the weight distribution is not conducive to good handling, with it being of the order of 70/30. The larger FSI / 1,2 spoiler only provides additional stability at higher speeds and lower drag, it does not offer downforce. I believe an OSS adds 35kg and that at the roof, which is incredibly bad for the car's centre of gravity.
I rode in an original A2 at the end of last year while I was in Eindhoven. That car had light 15" wheels but was running on original suspension, and it felt wooden and extremely stiff. My rental for that trip was a 2.0T Mondeo estate, which, being a Ford, was *really* nicely setup and extremely quick. It has a nice long wheelbase, was only wearing 16"s and was nicely new. The A2 wasn't. This experience concurs with the general consensus that the A2 is mildly oversprung, overdamped, and significantly underdamped on the rebound, such that the dampers don't push the wheels back down fast enough after being forced up (for example from a bump). This corresponds with the low weight of the car being a mild issue - it simply doesn't have the weight to push things around in the way, say, a Fiesta does. This explains the skippiness over sudden bumps taken at speed, whereas mild imperfections are OK. Large wheels exacerbate the problem (unsprung weight increases are significant) and lighter ones improve it. I felt that myself moving from 17,5kg / corner to 14,5.
What is also clear from both personal experience and anecdotal evidence is that tyre pressures make a simply massive difference to any perceived comfort, with 0,3 bar being the difference between a car that skips between bumps and one that actually sticks to the road with the resulting improvement in comfort from the tyres actually acting as part of the suspension. I originally put 2.4 / 2.7 into my 195/50R15s on 7J rims and the car was dangerously light on gravel. It was remarkably close to undrivable, but dropping to 2.1/2.3 made it actually quite good.
I will argue the following:
- light wheels make a huge difference to perceived comfort, all other things being equal
- the difference in pliancy between a 195/50 and 185/60 tyre is so significant that it cannot be dismissed
- tyre pressure has its place within that equation
The first is simple physics. Removing as much unsprung weight as possible allows the damper to work as effectively as it possibly can. That it increase fuel efficiency is a pleasant side-effect. The reason for the second and third is likely to be found in the damper rates and, because of the low mass on any one wheel, the significant impact any change on that one wheel can have. Driving with 22kg of 17" may also actually have an additional improvement in ride quality, because the tyre / wheel combination is so heavy it compensates for the light weight, especially when the damper is being pushed in. This may also help to explain the plethora of 17" 9 spokes with buckles - low profile, softer alloy and uncompromising dampers are probably a suboptimal combination for potholed roads.
Changing the dampers generally results in a better primary and secondary ride quality, where larger bumps (primary) are more absorbed and the secondary - damper control - improves along with it. The bigger question which is not answered involves the personal perception of quality of comfort. Personally, I cannot stand a poor primary ride. Large bumps should be felt in the cabin, and smaller ones should be felt as a minor, minor issue. I find the standard dampers - assuming underdampedness - cannot possibly provide this, since they're too hard to be pushed in and don't drop fast enough after the bump. I swapped mine out already after 7 years and 75000 kms.
The too-stiff springs add to the issue. The main reason for those is simple: in the aftermath of the A-Class Elktest debacle, it was essential that Audi was seen to be a safety-conscious manufacturer. For this reason there was the ESP testbed in the A2 factory with every single car's ESP being tested, the TTs were recalled for ESP retrofits and a spoiler, and the A2 springs are essentially too stiff. Part of the reason for the stiffness is also quite probably to avoid the perception that the car would tip, being relatively high and without a wide footprint. With the OSS weight added, this perception would be increased.
If we were following in the footsteps of the Elise, then at this point, the optimal solution would be to find springs which are around 20% - 25% softer than the originals, and then add to Bilstein B8s. This would give the compliance from the damper and allow the car to breathe with the road in a way it simply doesn't with the standard setup. A few years ago, we had a 307 SW. I drove the same (extremely bend-ridden) road in both cars shortly after one another and was extremely disappointed to find the A2 was less harmonic; it felt more like it was stiff and trying to pound the road into submission, where the 307 was allowing the road through and being more "diplomatic", for want of a better word. The 307 was more fun and faster.
The ARBs change the game slightly, but in a way I initially didn't expect. I am very aware of how worn suspension components get here in Finland in a relatively short space of time. Essentially, any set of droplinks can be considered dead after three years - even Meyle HD's: originals tend to survive maybe one winter - and dampers have a hard time. So I'm aware of the difference new droplinks make, increasing torsional stiffness at the front and influencing mildly the line through any given corner. The change induced with the Superpro dogbone is also of stiffness, with the immediacy of steering changes increasing. I cannot differentiate between this and the ARB, as they were done at the same time.
The combination of the new front ARB and the rear ARB changes the car in an interesting way. Torsional stiffness has been increased massively, but longitudinal not at all. The result of this is massively higher cornering speeds - and g-forces - but without the unpleasant roll. When driving into the drive, the car feels like it will happily "**** a wheel", even if it won't. But around roundabouts, speeds just went up by 5-10 km/h without me even thinking because I'm held in place by sports seats and don't really feel the G-forces. I essentially pushed my daughter into the door on Tuesday because I flicked right-left into a roundabout, we slid and it was all lateral, no roll. That was just with the rear ARB. Now? it will be even more extreme and I won't notice. I simply didn't realise when I started my test drive just how fast I was taking corners. For me, that's a great compliment. The feel is no different in terms of compliancy. Nodding when braking is essentially non-existent now, as is squat on take-off.
For my normal passengers, this is optimal. They can be shaken, they don't want to feel that they're in a boat.
I would say this is a massively effective upgrade to the standard; a basic setup would be the ARBs in conjunction with B4s, which, while stiffening dampers slightly, doesn't go anywhere near as far as the B8 setup I run.
Comparing to the Fiesta; it's a 3333km old July 2015 registered 1.0 EcoBoost Titanium, currently wearing 195/55R15s. Compliance is better than the A2, even at cold temperatures. But that compliancy is bought at the cost of roll, which makes it feel less comfortable and more susceptible to sidewinds. It also tracks slightly truer than the A2, and has a lot more grip, which I suspect is due to a badly setup camber / caster on the A2. Neither car is crashy over bumps, at 5-10C both are reasonably supple over imperfections but the perceived "hewn from rock" quota in the A2 is now massively higher. It also just goes around corners, where in the Fi I need to brake rather than lift.
So, to a perception of quality: in my eyes, compliancy is not important but very nice to have. Nod and squat are annoying rather than a problem. Roll is something I do not like, and neither do my passengers. So the ARBs provide a very nice solution to the issue of roll without compromising the other values of the suspension setup. I drive a lot of rentals for work and am happy that the new setup in the A2 hasn't compromised the relative comfort that was there, and I'm happy to compare the ride quality positively to those vehicles.
- Bret
I think this deserves a post of its own, because we end up looking at the term "comfort".
TL;DR version: in my eyes, suspension compliance is not important but very nice to have. Nod and squat are annoying rather than a problem. Roll is something I do not like, and neither do my passengers. So the ARBs provide a very nice solution to the issue of roll without compromising the other values of the suspension setup.
The rest of the post:
I'm living in a country where poor A- and B-Class roads are the ones I drive most frequently, so I need something that is stable at speed on suboptimal surfaces, allows me to drive gravel without compromising too much, and which corners nicely. The standard routes to the airport and the office are mainly motorway; to the northern office it's straight roads but much traffic and to the summer house it's three hours of poorly-asphalted curves with ludicrous quantities of bumps and hollows. To allow any confidence, the car needs to feel good and planted. The speed limits are generally low but not having to flick cruise off is a bonus.
The baseline has to be the original setup in an A2. The TDIs are slightly heavier over the front axle, and as a result have a slightly higher spring rate. This is mirrored with the FSI, whereas the 1.4 petrol has a lower spring rate. For any of the vehicles, the weight distribution is not conducive to good handling, with it being of the order of 70/30. The larger FSI / 1,2 spoiler only provides additional stability at higher speeds and lower drag, it does not offer downforce. I believe an OSS adds 35kg and that at the roof, which is incredibly bad for the car's centre of gravity.
I rode in an original A2 at the end of last year while I was in Eindhoven. That car had light 15" wheels but was running on original suspension, and it felt wooden and extremely stiff. My rental for that trip was a 2.0T Mondeo estate, which, being a Ford, was *really* nicely setup and extremely quick. It has a nice long wheelbase, was only wearing 16"s and was nicely new. The A2 wasn't. This experience concurs with the general consensus that the A2 is mildly oversprung, overdamped, and significantly underdamped on the rebound, such that the dampers don't push the wheels back down fast enough after being forced up (for example from a bump). This corresponds with the low weight of the car being a mild issue - it simply doesn't have the weight to push things around in the way, say, a Fiesta does. This explains the skippiness over sudden bumps taken at speed, whereas mild imperfections are OK. Large wheels exacerbate the problem (unsprung weight increases are significant) and lighter ones improve it. I felt that myself moving from 17,5kg / corner to 14,5.
What is also clear from both personal experience and anecdotal evidence is that tyre pressures make a simply massive difference to any perceived comfort, with 0,3 bar being the difference between a car that skips between bumps and one that actually sticks to the road with the resulting improvement in comfort from the tyres actually acting as part of the suspension. I originally put 2.4 / 2.7 into my 195/50R15s on 7J rims and the car was dangerously light on gravel. It was remarkably close to undrivable, but dropping to 2.1/2.3 made it actually quite good.
I will argue the following:
- light wheels make a huge difference to perceived comfort, all other things being equal
- the difference in pliancy between a 195/50 and 185/60 tyre is so significant that it cannot be dismissed
- tyre pressure has its place within that equation
The first is simple physics. Removing as much unsprung weight as possible allows the damper to work as effectively as it possibly can. That it increase fuel efficiency is a pleasant side-effect. The reason for the second and third is likely to be found in the damper rates and, because of the low mass on any one wheel, the significant impact any change on that one wheel can have. Driving with 22kg of 17" may also actually have an additional improvement in ride quality, because the tyre / wheel combination is so heavy it compensates for the light weight, especially when the damper is being pushed in. This may also help to explain the plethora of 17" 9 spokes with buckles - low profile, softer alloy and uncompromising dampers are probably a suboptimal combination for potholed roads.
Changing the dampers generally results in a better primary and secondary ride quality, where larger bumps (primary) are more absorbed and the secondary - damper control - improves along with it. The bigger question which is not answered involves the personal perception of quality of comfort. Personally, I cannot stand a poor primary ride. Large bumps should be felt in the cabin, and smaller ones should be felt as a minor, minor issue. I find the standard dampers - assuming underdampedness - cannot possibly provide this, since they're too hard to be pushed in and don't drop fast enough after the bump. I swapped mine out already after 7 years and 75000 kms.
The too-stiff springs add to the issue. The main reason for those is simple: in the aftermath of the A-Class Elktest debacle, it was essential that Audi was seen to be a safety-conscious manufacturer. For this reason there was the ESP testbed in the A2 factory with every single car's ESP being tested, the TTs were recalled for ESP retrofits and a spoiler, and the A2 springs are essentially too stiff. Part of the reason for the stiffness is also quite probably to avoid the perception that the car would tip, being relatively high and without a wide footprint. With the OSS weight added, this perception would be increased.
If we were following in the footsteps of the Elise, then at this point, the optimal solution would be to find springs which are around 20% - 25% softer than the originals, and then add to Bilstein B8s. This would give the compliance from the damper and allow the car to breathe with the road in a way it simply doesn't with the standard setup. A few years ago, we had a 307 SW. I drove the same (extremely bend-ridden) road in both cars shortly after one another and was extremely disappointed to find the A2 was less harmonic; it felt more like it was stiff and trying to pound the road into submission, where the 307 was allowing the road through and being more "diplomatic", for want of a better word. The 307 was more fun and faster.
The ARBs change the game slightly, but in a way I initially didn't expect. I am very aware of how worn suspension components get here in Finland in a relatively short space of time. Essentially, any set of droplinks can be considered dead after three years - even Meyle HD's: originals tend to survive maybe one winter - and dampers have a hard time. So I'm aware of the difference new droplinks make, increasing torsional stiffness at the front and influencing mildly the line through any given corner. The change induced with the Superpro dogbone is also of stiffness, with the immediacy of steering changes increasing. I cannot differentiate between this and the ARB, as they were done at the same time.
The combination of the new front ARB and the rear ARB changes the car in an interesting way. Torsional stiffness has been increased massively, but longitudinal not at all. The result of this is massively higher cornering speeds - and g-forces - but without the unpleasant roll. When driving into the drive, the car feels like it will happily "**** a wheel", even if it won't. But around roundabouts, speeds just went up by 5-10 km/h without me even thinking because I'm held in place by sports seats and don't really feel the G-forces. I essentially pushed my daughter into the door on Tuesday because I flicked right-left into a roundabout, we slid and it was all lateral, no roll. That was just with the rear ARB. Now? it will be even more extreme and I won't notice. I simply didn't realise when I started my test drive just how fast I was taking corners. For me, that's a great compliment. The feel is no different in terms of compliancy. Nodding when braking is essentially non-existent now, as is squat on take-off.
For my normal passengers, this is optimal. They can be shaken, they don't want to feel that they're in a boat.
I would say this is a massively effective upgrade to the standard; a basic setup would be the ARBs in conjunction with B4s, which, while stiffening dampers slightly, doesn't go anywhere near as far as the B8 setup I run.
Comparing to the Fiesta; it's a 3333km old July 2015 registered 1.0 EcoBoost Titanium, currently wearing 195/55R15s. Compliance is better than the A2, even at cold temperatures. But that compliancy is bought at the cost of roll, which makes it feel less comfortable and more susceptible to sidewinds. It also tracks slightly truer than the A2, and has a lot more grip, which I suspect is due to a badly setup camber / caster on the A2. Neither car is crashy over bumps, at 5-10C both are reasonably supple over imperfections but the perceived "hewn from rock" quota in the A2 is now massively higher. It also just goes around corners, where in the Fi I need to brake rather than lift.
So, to a perception of quality: in my eyes, compliancy is not important but very nice to have. Nod and squat are annoying rather than a problem. Roll is something I do not like, and neither do my passengers. So the ARBs provide a very nice solution to the issue of roll without compromising the other values of the suspension setup. I drive a lot of rentals for work and am happy that the new setup in the A2 hasn't compromised the relative comfort that was there, and I'm happy to compare the ride quality positively to those vehicles.
- Bret
timmus
A2OC Donor
Hi Steve (and others!),
Yes, what you've written is true, but it fails to take a specific scenario into account...
When encountering road undulations and bumps that are perpendicular to the direction of travel and span the width of the road (or at least the width of your car's track), you will feel no difference from a stiffer ARB. However, if you hit a bump or a pot hole with just one wheel, the stiffness of the ARB does affect comfort. Since the ARB couples the left- and right-side springs, the torsion of the ARB effectively increases the spring rate for that individual wheel.
There are a lot of very rough roads around where I live, and indeed throughout a lot of rural Britain. I do have my concerns that it's going to increase jitteriness.
Cheers,
Tom
Yes, what you've written is true, but it fails to take a specific scenario into account...
When encountering road undulations and bumps that are perpendicular to the direction of travel and span the width of the road (or at least the width of your car's track), you will feel no difference from a stiffer ARB. However, if you hit a bump or a pot hole with just one wheel, the stiffness of the ARB does affect comfort. Since the ARB couples the left- and right-side springs, the torsion of the ARB effectively increases the spring rate for that individual wheel.
There are a lot of very rough roads around where I live, and indeed throughout a lot of rural Britain. I do have my concerns that it's going to increase jitteriness.
Cheers,
Tom
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Birchall
Dick Chown Award 2016
As I said, firsthand experience as in your case is very useful, and that is a large ARB, NICE.
Everytime I see pictures of your car I am VERY impressed, I REALLY like it.
Steve B
Birchall
Dick Chown Award 2016
Hi Tom,
That is exactly what I said, but I think I used far too many words and so it was not that easy to read it top to bottom.
I can see why you asked , I have driven the roads in your area and there are not many that are silky smooth and level, so your ride comfort will be affected, hence your question. I did say the above was not aimed at you.
Steve B
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timmus
A2OC Donor
You did indeed, and my reply wasn't meant to contradict anything you said. I couldn't at first find your explanation of the above scenario, but it is there now I look.
The one thing I'd say is that it's not quite a best-of-both worlds. There are undoubtedly a raft of advantages - I did buy a kit after all! - but such things are rarely without a trade-off in some other area. As you point out yourself, Audi don't fit ARBs like the H&R as standard in order to keep things more comfortable.
Cheers,
Tom
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Birchall
Dick Chown Award 2016
My fault for using too many words, it is a failing of mine.
My books are the same (very wordy) but they are meant to be I think!
Steve B
bretti_kivi
Member
Hi,
I'll disagree slightly. The H&R is a good 6mm in diameter larger than the original equipment, so it's torsionally significantly stiffer. This is, however, only really noticeable with body roll and I can't say I noticed any significant difference in compliance from before or after the front change. The original ARB is also of the same dimensions as those used in Polos and Seats, so I'm sure there's a certain amount of "if it's good enough for them..." involved.
But then again, most are driving around on ancient, broken plastic collars with the chorus of clunks to accompany. I've no idea how this applies to you, but I understand what difference the new polo rubbers make and the H&R is a tick stiffer again (yes, also using SuperPro bushes there) than a fresh set of rubbers on a late-model ARB (M revision).
That the rear ARB wasn't done is probably down to two / three things:
- additional cost for improvement over and above "good enough" was too high.
- additional cornering capability was unwanted
- the wrong image for the car if it was seen / felt to be a sportsmobile when the 3L was very high on the agenda
I think the resolution has to come down to your perception of comfort. I am personally willing to sacrifice a certain amount of pliancy for a lack of roll. Some of that pliancy can be regained through smart choices in terms of wheels, wheel size, and the like, but, yes, there is a compromise. I personally don't feel the comfort now as being lower than on clapped-out FSDs, but that's also a matter of taste and priorities.
- Bret
chubbybrown
Member
bretti_kivi
Member
... well, the dogbones were made available by Nuerne on the German forums and I picked up the complete package. This was part of the superpro pack (total content: ARB mounts, rack mount, rear axle bushes, dogbone).
My old one was very, very worn, after around 6 years. Note, please, that they do transmit *far more* vibration through to the cabin at tickover and that needs be considered. You will also need a press of some variety to get these things in place.
- Bret
My old one was very, very worn, after around 6 years. Note, please, that they do transmit *far more* vibration through to the cabin at tickover and that needs be considered. You will also need a press of some variety to get these things in place.
- Bret
Last edited:
bretti_kivi
Member
I'll reiterate the above to push a point regarding softer dampers, springs and larger tyres.
All other things being equal:
- Weightier tyres will make ride worse. They are unsprung weight, which makes it significantly harder for the damper to control - the mass is out, well away from the fulcrum, so more effort is needed to control
- higher sidewalls will provide more "give" if the profile allows it, but it is only ever squidge and not control
- stiffer springs will induce more bunny hop and skittishness
- softer dampers cannot provide control. Control can only come from a grip on the body of the car, so from a strong damper
- "sportiness" generally gets defined as a lack of roll, nod and squat. A lack of body movement permeates the car.
- a "softer" car will slide earlier, harder, and be more difficult to control (and I'm happy to prove this one on the ice)
The two diametric opposites of teh handling spectrum:
1)
- insufficient damping
- hard springs
- heavy wheels
vs
2)
- fully controlled body damping, especially on the rebound
- softer springs
- light wheels
in scenario 1), your heavy wheels hit a bump. They are pushed up with the forces involved, which are bigger because the wheel is heavier. Now the spring tries to absorb but cannot, because it's stiff, so the movement is not passed to the damper. And so you jump.
with 2), the light wheel pushes a much smaller load to the spring, which allows the damper to work.
Stiffer springs are fine when combined with capable damping. Softer springs give a way better ride but don't need softer dampers, they, if anything, need more control.
As regards sliding: currently we have truly bad road conditions even by our standards. The Fi slides much earlier and longer than the A2. The A2 is wearing mildly smaller tyres - 185/60R15 vs 195/55R15 - and it's relatively stiff. The slide is gradual and relatively short in the A2, the Fi keeps going. ESP is on on both cars. Both have relatively new suspension.
Having driven the A2 recently to work (the first big trip since the ARB work), I'm impressed. It's planted in a way I haven't experienced in years, and that's on 185 studded winter tyres. It has approx zero body roll on any transition; where the expansion joints across the road would previously be bone-jarring, they are now simply a "dump-dump" with minimal movement. The winter rims are Rial Milanos, so not very light, but not heavy, either. I'd estimate around 16kg wheel / tyre combo, where the summers are around 13kg, I believe.
The compliance is down slightly, but I can feel the win everywhere else. It's nice to be behind the wheel of a car that really inspires confidence.
I'll state what's slowly becoming very clear for me: the way for really good roadholding and comfort lies with controlled damping and soft-ish springs. OEM or similar, combined with as light wheels as possible.
- Bret
PS: some spring rates are listed here: https://a2-freun.de/forum/showthread.php?t=46362