[M-Pilot]

I've been running Ohlins R/T on my M2C for about a year now and I'm still confused by couple things in the instructions manual. Additionally, I'm also still experiencing some issues with the ride comfort.

Firstly, I want to ask how the rear ride height is adjusted. According to the image below, the height adjuster is on the strut and spring perch is only for preload:



However, my shop during the install kept telling me that the only way to adjust the ride height was to play with the spring perch. I didn't initially believe it as it contradicts with the manual. However, Brian from Ohlins replied to my email in a similar way:

"The static ride height must be set using the spring adjuster as the shop has performed. Preload, for this situation, is set by the shock length as the shock is what’s maintaining tension on the spring while in full droop.



The height adjuster is not on the shock body. The height adjuster is the spring preload adjuster in this case.



An example of this being true is if you lengthened the shock via the lower gold cup. This would not affect the static height of the car – it would only reduce bump travel of the damper and reduce tension on the spring while in full droop."

If the spring perch is the height adjuster in this case, what does the "height adjuster" on the strut do? Really confused about this issue and it's driving me crazy. In my opinion, installation instructions provided by Ohlins aren't clear at all.

Another thing is the ride quality... I have their recommended spring rates (90 front and 190 rear). Even though they phenomenal at the track, I find the rear to be extremely stiff for street use. I tried using different stiffness (15 to 20 clicks) and still very bouncy/jumpy on bumpy roads. I just someone's comment on how to describe the situation so I'll use the same words... Even on highway, at certain dips or bumps, it launches me out of my seat and I'm not exaggerating. If it's this uncomfortable for the driver, it's usually significantly worse for the passenger. I definitely wouldn't wanna be a rear passenger in my car. I wanted to post about this issue because I have read so many posts on how much better Ohlins is than the stock suspension when it comes to ride quality. Maybe I should switch to 70/160 spring rates.

Anyone else experienced similar problems with Ohlins or does anyone have any recommendations?

[PLF69]

Altrough winter just arrived around here I am supposed to reveive my 70/140 setup soon, I'll report back when its installed and I've ridden in the car etc.

[Caduceus]

In my opinion, Ohlins have labelled the two adjusters the wrong way around and this is the cause of your confusion. On the supplied diagram, the “Spring preload adjuster” actually raises and lowers the height of the vehicle at the rear. This is quite obvious.

The purpose of the second adjuster located on the body of the shock is to make sure the spring remains under tension when the suspension is at full droop (for example, when jacked up or if airborne ;-) ). If the shock is allowed to lengthen too much in these scenarios, the spring will become loose and could potentially fall out of the retaining plugs at the top or bottom. So in other words, it is to make sure some preload remains on the spring.

So to set yourself up correctly:

1) measure the height of the suspension with the weight on the wheels. Let’s say you want to go 20mm lower than you currently are.

2) Jack the car up and adjust the spring perch towards the body of the car by 20mm. Assuming there is enough adjustment available. If it bottoms out, that is as low as you are going to be able to go. The spring perch is the thing Ohlins have called the “spring pre-load adjuster” but as I have explained, it will change the height of the vehicle.

3) Drop the car back onto its wheels and confirm you are happy with the new height.

4) Jack the car up again (by the body, not any part of the suspension or subframe) and allow the wheel to hang as low as it will go (full droop). Grab the spring and give it a good push-pull. There is probably still some tension on it. If it rattles around, there is zero pre-load on it and you can skip the next step.

5) Now wind what Ohlins call the “height adjuster” (on the body of the shock) out to lengthen the shock. Keep going until the spring just starts to become loose as it reaches full expansion. You are now at zero pre-load. If you go too far and it starts to rattle around, snug it up a bit until it is just starting to make contact.

6) Take Ohlins advice on recommended pre-load. Let’s say it is 40mm (I don’t know the actual value - this is an example only). Wind the “height adjuster” in the direction that shortens the overall length of the shock. This will start to compress (pre-load) the spring. Keep going for 40mm (or whatever value you are using). Pre-load is now set.

7) Drop the car back onto its wheels and recheck the ride height. The adjustments you made at step 5 and 6 should have made no difference to the height you achieved at the end of step 3.

I hope this helps. If the diagram was labelled the other way around, I don’t think you would have been confused. I wonder if this is just a publication error or whether something got lost in translation from Swedish?

[FaRKle!]

I've only played around with R&T on the F32, but I can't imagine it's much different than on your F87. The spring adjuster is what determines the ride height. When the car is on the ground and loaded the spring is what supports the car, so lengthening/shortening that assembly is what controls the height.

Preload, for this situation, is set by the shock length as the shock is what’s maintaining tension on the spring while in full droop.

When you get to really high spring rates (like in this kit) the weight of the car doesn't compress the springs very much (less than an inch in your case), thus Ohlins is probably using the damper/shock length to limit the amount of droop (suspension unloading) per their statement to you. If you set the rear spring height adjuster to "all the way up" or to the lowest ride height, and disconnect the shock, I'll bet the spring will be loose with the car up in the air. In a situation where the damper/shock body isn't adjusted it's possible for the spring to become loose and unseated if droop isn't controlled while driving. Other companies combat this by either using a progressive rate spring (like Bilstein), where the low spring rate coils only come into play during droop, or by using helper springs, which also keep the main spring seated during droop events.

The spring rates don't look terrible to me, but I'd recommend lowering the front spring rate to have a higher rear ride frequency over the front. This will help the car settle faster over road features and make it feel more stable. The F32 front rate of 60N/mm would probably work well for you (for reference that kit uses a 160N/mm rear spring). Too many people only see the "scary" high rear spring rate number and think that's the one they need to lower.

When I was dialing in my friend's F32 R&T dampening the recommended Ohlins settings were too overdamped. That can cause the ride to be too stiff and harsh, per what you're experiencing. Part of that is because the dampers are rebound biased, so they don't return to neutral height as fast as they get compressed. When that happens you get pulled into the bump stops, which add additional spring rate and pop you back off. It also prevents the wheel from recovering as quickly over features like track curbing so you have less traction overall. For my friend's car we paid attention to how harsh each end of the car felt going over features at speed, and then turned down the dampening accordingly. In his case, the rear felt harsher than the front, so we lowered that by a greater amount. This drastically smoothed out his ride, and he was able to have a more comfortable daily driver, as well as use all the track at the track since the suspension was better able to handle the curbing and maintain traction. At our last outing two weeks ago a lot of other drivers at the track were commenting on how the curbing at certain turns was harsher than in prior years. We just laughed because our suspension were dialed in and able to handle those features smoothly, thus allowing us to attack them with greater speed. Stiff isn't fast, but smooth and controlled is.

[Caduceus]

Excellent post, Farkle. We are on the same page and posted at almost the same time.

[FaRKle!]

Originally Posted by Caduceus

Excellent post, Farkle. We are on the same page and posted at almost the same time.

You laid out the adjustment methodology very well and clearly!


One tip I have to offer is for the rear, the spring motion ratio is on the order of 0.589 to the wheel, so if you want to raise/lower by X amount at the wheel, the amount of adjustment needed at the spring is X * 0.589. The front motion ratio is almost 1, so no need to really do any math there.

[M-Pilot]

Caduceus and FaRKle!, can't thank you guys enough! Finally understand how it works and it makes total sense. I just need to either explain this whole thing to my shop or find a place that knows all this stuff. Again, really appreciate both answers!

[M-Pilot]

Originally Posted by Caduceus

6) Take Ohlins advice on recommended pre-load. Let’s say it is 40mm (I don’t know the actual value - this is an example only). Wind the “height adjuster” in the direction that shortens the overall length of the shock. This will start to compress (pre-load) the spring. Keep going for 40mm (or whatever value you are using). Pre-load is now set.

So for this step, what's the best practice in general? Should I stick to Ohlins recommended preload which is 40mm as you said or is there another way to come up with a right preload number? (Also, just to confirm, based on what I have read so far, the preload is set using the shock body in this case, right? )

[FaRKle!]

Originally Posted by cntzl

Caduceus and FaRKle!, can't thank you guys enough! Finally understand how it works and it makes total sense. I just need to either explain this whole thing to my shop or find a place that knows all this stuff. Again, really appreciate both answers!

I'd be a bit wary if your shop isn't already familiar with this concept since it's not that uncommon and other coilovers (like BC) use similar methods. Just across the Bay from you, Edge Motorworks in Fremont has always done a quality job for me. I assume you're looking for a place to adjust the ride height and corner balance too, right?

Originally Posted by cntzl

So for this step, what's the best practice in general? Should I stick to Ohlins recommended preload which is 40mm as you said or is there another way to come up with a right preload number? (Also, just to confirm, based on what I have read so far, the preload is set using the shock body in this case, right? )

The Ohlins instructions have a standard preload (5mm) mentioned in the front strut assembly section, but don't have one mentioned for the rear. It's likely you can use the same value though. What this means is after you dial in your ride height, adjust the damper length such that at its longest, the lower camber arm droop is limited such that the spring is still compressed by 5mm.

[M-Pilot]

Originally Posted by FaRKle!

I'd be a bit wary if your shop isn't already familiar with this concept since it's not that uncommon and other coilovers (like BC) use similar methods. Just across the Bay from you, Edge Motorworks in Fremont has always done a quality job for me. I assume you're looking for a place to adjust the ride height and corner balance too, right?

The Ohlins instructions have a standard preload (5mm) mentioned in the front strut assembly section, but don't have one mentioned for the rear. It's likely you can use the same value though. What this means is after you dial in your ride height, adjust the damper length such that at its longest, the lower camber arm droop is limited such that the spring is still compressed by 5mm.

Believe it or not, my suspension was installed by one of the most reputable BMW shops in the Bay but the tech who did the install was new and wasn't really familiar with it. At the end, I just gave up and left everything as it came out of the box, meaning the spring perch is set to 40mm (same as the pic above) and my rear shock has the preload that came with it (the tech couldn't even break loose the nut on the shock body). What's interesting is that I have a friend who has the exact same car and coilover kit. I showed him this thread and he's just as surprised as me because his experience is the exact opposite. His car is even slightly lower than mine and he's running even stiffer settings (11-12 clicks in the rear) but he doesn't have any of this ride comfort issues that I'm experiencing. His was installed by the same shop by a different tech. This has been really frustrating for me to say the least...

[jashton]

Originally Posted by cntzl

Believe it or not, my suspension was installed by one of the most reputable BMW shops in the Bay but the tech who did the install was new and wasn't really familiar with it. At the end, I just gave up and left everything as it came out of the box, meaning the spring perch is set to 40mm (same as the pic above) and my rear shock has the preload that came with it (the tech couldn't even break loose the nut on the shock body). What's interesting is that I have a friend who has the exact same car and coilover kit. I showed him this thread and he's just as surprised as me because his experience is the exact opposite. His car is even slightly lower than mine and he's running even stiffer settings (11-12 clicks in the rear) but he doesn't have any of this ride comfort issues that I'm experiencing. His was installed by the same shop by a different tech. This has been really frustrating for me to say the least...

For reference - my strut length out of the box, using the instructions measuring technique, was 505mm on both. I adjusted mine to 497mm for my setup as I mentioned to you yesterday.

[ddk632]

Are you sure your installer was counting the clicks correctly, clockwise from underneath the car facing up, like any screw, all the way left is full close. Count clicks clockwise or to the right from there. All 4 wheels the same way!

My installer had a confusion about the direction of "clockwise" for the rear and thus I ended up with 10 clicks front and 20 rear which caused the pogo stick launching out of the seat effect.

Just a thought to add if everything else is correct this might be the issue.

[M-Pilot]

Originally Posted by ddk632

Are you sure your installer was counting the clicks correctly, clockwise from underneath the car facing up, like any screw, all the way left is full close. Count clicks clockwise or to the right from there. All 4 wheels the same way!

My installer had a confusion about the direction of "clockwise" for the rear and thus I ended up with 10 clicks front and 20 rear which caused the pogo stick launching out of the seat effect.

Just a thought to add if everything else is correct this might be the issue.

Clicks are not an issue. I first close it (full stiff) then open it up (count the clicks). Closing/full stiff is no different than tightening a water bottle cap that is positioned up side down. I do it before and after each track day and experimented up to 2 clicks in the front and 4 clicks in the rear (which would be brutal for the street). So I'm pretty confident the way I change the clicks (the shop did it the same way right after the install as well). If clicks were the issue changing to a lower number of clicks, which I already tried, would give me a softer ride.

[M Fifty]

Maybe you're just running out of suspension travel? Would need a significant mismatch of spring length/rate, shock length and preload, but its possible.

Otherwise, did they re-index the the suspension bushes? Shouldn't be a problem with only 10mm lower, but...

[M-Pilot]

Originally Posted by M Fifty

Maybe you're just running out of suspension travel? Would need a significant mismatch of spring length/rate, shock length and preload, but its possible.

Otherwise, did they re-index the the suspension bushes? Shouldn't be a problem with only 10mm lower, but...

Honestly, I'm clueless at this point... This is Ohlins recommended/default spring rate. I haven't changed the springs at all. I don't think they re-indexed the suspension but not sure if it would cause this much drama. Ohlins now recommending me to run 25 clicks in the rear, which is not a big deal, I can definitely try but while others are running 11-12 clicks in the rear comfortably, it just makes me think what's going on with mine. I'm also not a person who's too much focused on ride comfort. I can definitely tolerate a very stiff ride (as I did in my M4) but being launched out of my seat at certain dips and bumps is a bit too much.

[ddk632]

Originally Posted by cntzl

Clicks are not an issue. I first close it (full stiff) then open it up (count the clicks). Closing/full stiff is no different than tightening a water bottle cap that is positioned up side down. I do it before and after each track day and experimented up to 2 clicks in the front and 4 clicks in the rear (which would be brutal for the street). So I'm pretty confident the way I change the clicks (the shop did it the same way right after the install as well). If clicks were the issue changing to a lower number of clicks, which I already tried, would give me a softer ride.

Gotcha. It has caught a few people out, including myself, so thought was worth a mention.

Btw softer ride is higher number of clicks, not lower....

[M-Pilot]

Originally Posted by ddk632

Gotcha. It has caught a few people out, including myself, so thought was worth a mention.

Btw softer ride is higher number of clicks, not lower....

Yes, I know. All I was saying is, if I had mixed up the direction of the clicks, I would have gotten a softer ride with lower number of clicks, which is not the case. But thanks anyways!

[Megator]

Originally Posted by cntzl

Believe it or not, my suspension was installed by one of the most reputable BMW shops in the Bay but the tech who did the install was new and wasn't really familiar with it. At the end, I just gave up and left everything as it came out of the box, meaning the spring perch is set to 40mm (same as the pic above) and my rear shock has the preload that came with it (the tech couldn't even break loose the nut on the shock body). What's interesting is that I have a friend who has the exact same car and coilover kit. I showed him this thread and he's just as surprised as me because his experience is the exact opposite. His car is even slightly lower than mine and he's running even stiffer settings (11-12 clicks in the rear) but he doesn't have any of this ride comfort issues that I'm experiencing. His was installed by the same shop by a different tech. This has been really frustrating for me to say the least...

Maybe get the guys who installed your friends kit to look at your? or take some measurements off of his kit?

Assuming everything is in good working order wouldn't too much preload on the rear give a crappy bouncy ride since you need to overcome whatever preload force the spring is already exerting outwards before compressing it?

Ie at 190N/mm a preload of 40mm gives a preload force of 7600N or roughly 775KG. Assuming 1/4 the weight is on each rear wheel (say 400KG) and a spring motion ratio of 0.6 (then the "weight" on the spring is roughly 670KG ) the the spring is still pushing the car upwards with 100KG of force which needs to be overcome before the spring compresses due to any dynamic forces.

I imagine the numbers work out so you have some compression of the shock at rest but not much this means you have no or very little extension travel which would seem to make the car handle like crap over potholes. It also means bumps are not absorbed as the body will be lifted before the spring can be compressed further, again leading to a crappy ride.

The damper settings would not affect the ride much as they do not work unless the spring allows the suspension to move.

This is just my thought experiment and I have no real world experience setting up suspensions. A quick check would be to jack the car and see how much the suspension drops by. If it is less than your friends this might be the culprit no?

Can the experts tell me if I am way off?

[FaRKle!]

Originally Posted by Megator

Maybe get the guys who installed your friends kit to look at your? or take some measurements off of his kit?

Assuming everything is in good working order wouldn't too much preload on the rear give a crappy bouncy ride since you need to overcome whatever preload force the spring is already exerting outwards before compressing it?

Ie at 190N/mm a preload of 40mm gives a preload force of 7600N or roughly 775KG. Assuming 1/4 the weight is on each rear wheel (say 400KG) and a spring motion ratio of 0.6 (then the "weight" on the spring is roughly 670KG ) the the spring is still pushing the car upwards with 100KG of force which needs to be overcome before the spring compresses due to any dynamic forces.

I imagine the numbers work out so you have some compression of the shock at rest but not much this means you have no or very little extension travel which would seem to make the car handle like crap over potholes. It also means bumps are not absorbed as the body will be lifted before the spring can be compressed further, again leading to a crappy ride.

The damper settings would not affect the ride much as they do not work unless the spring allows the suspension to move.

This is just my thought experiment and I have no real world experience setting up suspensions. A quick check would be to jack the car and see how much the suspension drops by. If it is less than your friends this might be the culprit no?

Can the experts tell me if I am way off?

It looks like you're getting confused by Ohlin's terminology too. When they say "40mm of pre-load" they don't actually mean the spring is compressed 40mm at neutral ride height. If that were true the spring would basically never move under normal operating conditions since the weight of the car only compresses it by about 16mm on its own.

What Ohlins means is that the space between the top of the rear adjuster and the top of the spring needs to be 40mm in order to preload the spring by a small amount (let's say 5mm) to prevent it from coming loose/popping out under the droop allowed by the damper body at the length settings for that they also recommend. I agree it's not very straight forward.

[M Fifty]

If you're being fired out of the seat over humps and bumps, it suggests you're running out of rebound travel. Remind me - how high is your car sitting (measuring from the top of the underside of the wheel arch to the lowest point on the bottom edge of the wheel)?

[Megator]

Originally Posted by FaRKle!

If that were true the spring would basically never move under normal operating conditions since the weight of the car only compresses it by about 16mm on its own.


What Ohlins means is that the space between the top of the rear adjuster and the top of the spring needs to be 40mm in order to preload the spring by a small amount (let's say 5mm) to prevent it from coming loose/popping out under the droop allowed by the damper body at the length settings for that they also recommend. I agree it's not very straight forward.

I meant 40mm of preload ie compressing the spring by 40mm from its resting position.

I did pick this value from the one being discussed as it seems like an easy mistake to make and to wrongly set the preload to 40mm. I was asking if doing so would lead to your bolded statement above and whether this might be the culprit for the poor ride and suggested this should be checked.

What seems to be missing from Ohlins instructions is what the rear preload should be.

If the car compresses the springs by 16mm due to its weight then as I understand it you only have 16mm of extension if the preload is set to 0. Further increasing the preload would lead to an extension of the shock for the same applied weight which reduces the available extension travel.

This would seem to lead to traction problems over bumps and potholes as the suspension can only decompress so little and compressing requires overcoming the "excess" preload.

To summarise it would seem that the spring rate might be too high (not enough compression due to the weight) or the preload is to high, which leads to not enough extension (rebound? not sure on the term if it is from rest out) travel.

Or? and thanks for your reply

[Megator]

edit: double post