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      10-07-2020, 04:35 AM   #23
David.m
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Quote:
Originally Posted by iBrakeLate View Post
Just an update on this.

We've been talking to Ohlins about the issue with the vehicle dynamics. Did some measurements of the suspension, droop length, rear shock shaft measurements etc... It looks like unfortunately their instruction manual and the setup guide is quiet a bit off. The car doesn't have enough droop, preload is way off too.

As per the setup from the installation manual, the preload is set more than what it is supposed to be which could also be contributing to all of this.

I have a busy week this week, but we are going to make the changes Ohlins has recommended and report back.
Interested in what changes were suggested & how they go.

When I installed my Ohlins R&T I adjusted the shock length with the spring out so I could have max compression with the tyre not contacting wheel arch lining (at the time I had 285/35 PS4s), measuring from the bottom lip of 437M to top lip of guard was 545mm (car weight on Ohlins shock bump stop), full droop in this setting is 675mm. Looking at my notes I think the shock length was 510mm (where the instructions say 500), I'm just not 100% I recorded the shock length accurately

Just for interests sake the oem shock/bump stop allowed 15mm less compression travel, I was after more as on our bad country roads it wasn't uncommon to bottom out badly and the rebound was very unsettling.

I believe pre-load just determines ride height and I varied from the instructions as I didn't want the full 10mm drop from oem (& my rear springs at 160Nm), unfortunately I didn't write down my pre-load but I'm lowered around 6mm.
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      10-12-2020, 07:43 AM   #24
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Quote:
Originally Posted by David.m View Post
Interested in what changes were suggested & how they go.

When I installed my Ohlins R&T I adjusted the shock length with the spring out so I could have max compression with the tyre not contacting wheel arch lining (at the time I had 285/35 PS4s), measuring from the bottom lip of 437M to top lip of guard was 545mm (car weight on Ohlins shock bump stop), full droop in this setting is 675mm. Looking at my notes I think the shock length was 510mm (where the instructions say 500), I'm just not 100% I recorded the shock length accurately

Just for interests sake the oem shock/bump stop allowed 15mm less compression travel, I was after more as on our bad country roads it wasn't uncommon to bottom out badly and the rebound was very unsettling.

I believe pre-load just determines ride height and I varied from the instructions as I didn't want the full 10mm drop from oem (& my rear springs at 160Nm), unfortunately I didn't write down my pre-load but I'm lowered around 6mm.
We set the preload which determined the ride height of the rear. It lowered the car definitely more than the 10mm which their instruction says. Because when you put preload you are actually changing the spring rate as well, making it higher.

Then set the car down, drove around the block to get the suspension to settle and put the car on the 4 post lift.

The rear shock that is provided by Ohlins has 99mm travel. They wanted to see 55% compression travel, 45% droop travel. This is fairly easy to set if you have a 4 post lift.

With the car on the 4 post lift, I measured the rod length which is showing while the car is sitting still, which gives you the compression travel. remember you need to measure including the bump stop.

If you need to make adjustments to the shock height, every turn is 1.5mm in length.

Once I made the adjustments, again drove around the block to let the suspension settle, came back put the car on the 4 post lift and measured again. I am currently at %54 compression to 46% droop, which is close enough.
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      10-12-2020, 07:44 AM   #25
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For those who are interested, here is a video explaining the changes that were made, and you can see the rear of the car sits much lower now compared to the way Ohlins recommended specs would have it sit.

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      10-12-2020, 01:47 PM   #26
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Just uploaded the video from yesterday, the track condition wasn't that good since three corners were compromised because of puddles, but the car is behaving much better in the video.

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      10-12-2020, 05:49 PM   #27
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Quote:
Originally Posted by iBrakeLate View Post
Just uploaded the video from yesterday, the track condition wasn't that good since three corners were compromised because of puddles, but the car is behaving much better in the video.

Ahhhh PBIR!!!! That back straight is brutal in Formula 2000 car topping out at about 113!

Were you able to run about the same pace between those two sessions you are referencing even with the wet & dry conditions? Are you set up to run telemetry?
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      10-12-2020, 06:50 PM   #28
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Quote:
Originally Posted by OG Shark View Post
Ahhhh PBIR!!!! That back straight is brutal in Formula 2000 car topping out at about 113!

Were you able to run about the same pace between those two sessions you are referencing even with the wet & dry conditions? Are you set up to run telemetry?
Brutal long probably doing just 113! With the M2C I was hitting 147mph according to the GPS logs!

Running telemetry from OBD2 right now, which has not the greatest sampling rates. I will eventually hard wire the CANBUS cable.

The first video I posted on there wasn't too bad, even though most people get scared with a little bit of a drizzle, the track has a lot of heat and grip even with the light drizzle.

I think the conditions were more favorable the first time I was out while the car was having the corner exit issues.

Lap times were very comparable, however as you can see from both videos, with the new setup I wasn't pushing crazy since 3 of the corners were compromised due to standing water.

If I can make it out this week, I will definitely be back to see if I can put down some hot laps with the track fully dry. But all this rain we are getting isn't really helping to keep rubber on the track to keep it fast.

Last edited by iBrakeLate; 10-19-2020 at 05:16 PM..
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      10-17-2020, 12:10 PM   #29
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More updates on this, with the new settings that Ohlins recommended the car is a bit better but as the tires wear, still running into similar issues, just not as bad. After spending another day at the track trying to get a feel as to what is going on and what to do, I was lucky enough to have a pro driver who has a lot of experience give me his thoughts.

The main issue he noted is that the spring rates that Ohlins supplies with this kit is way too stiff, 90N/mm front (~513 lbs/in) and 190 N/mm rear ( ~1084 lbs/in).

Just ordered 70N/mm front (~399.71 lbs/in) and 120 N/mm (685.21 lbs/in) springs.

Also will be switching up the tires too, the A052's sidewalls are too soft, going to try the Nankang AR1's.

I will update this thread once I have some more information, might be useful for those who track their M2C and want to have an idea of a better setup to run than out of the box stuff Ohlins offers.
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      10-17-2020, 09:03 PM   #30
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Quote:
Originally Posted by iBrakeLate View Post
More updates on this, with the new settings that Ohlins recommended the car is a bit better but as the tires wear, still running into similar issues, just not as bad. After spending another day at the track trying to get a feel as to what is going on and what to do, I was lucky enough to have a pro driver who has a lot of experience give me his thoughts.

The main issue he noted is that the spring rates that Ohlins supplies with this kit is way too stiff, 90N/mm front (~513 lbs/in) and 190 N/mm rear ( ~1084 lbs/in).

Just ordered 70N/mm front (~399.71 lbs/in) and 120 N/mm (685.21 lbs/in) springs.

Also will be switching up the tires too, the A052's sidewalls are too soft, going to try the Nankang AR1's.

I will update this thread once I have some more information, might be useful for those who track their M2C and want to have an idea of a better setup to run than out of the box stuff Ohlins offers.
Interesting. I find the springs a bit on the soft side on track. Car bottoms on compressions in the rear. I致e actually been considering stiffer springs for the rear if I stick with the staggered wheel/tire package to also get a bit less understeer, or all around if I go back to square.

I値l be interested to hear how those rates work for you though. I know TC Kline recommends significantly softer rates with his coilovers.

Maybe I知 thinking about this wrong.
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      10-19-2020, 01:15 AM   #31
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Originally Posted by bentom2 View Post
Interesting. I find the springs a bit on the soft side on track. Car bottoms on compressions in the rear. I致e actually been considering stiffer springs for the rear if I stick with the staggered wheel/tire package to also get a bit less understeer, or all around if I go back to square.

I値l be interested to hear how those rates work for you though. I know TC Kline recommends significantly softer rates with his coilovers.

Maybe I知 thinking about this wrong.
Check to make sure the car has the correct amount of compression travel for the rear shock. Kind of hard to believe it would bottom out with the correct amount of shock length set.

I get tire rub in the back on very very big bumps/dips in a construction zone. On track it is no where near getting to that level of compression travel.
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      10-19-2020, 10:55 AM   #32
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Quote:
Originally Posted by iBrakeLate View Post
Check to make sure the car has the correct amount of compression travel for the rear shock. Kind of hard to believe it would bottom out with the correct amount of shock length set.

I get tire rub in the back on very very big bumps/dips in a construction zone. On track it is no where near getting to that level of compression travel.
Maybe a poor choice of words on my part; I’m reaching the bump stops more than I’d like, which depending on the tires I’m running, also means I get some pretty significant tire rub.

I might be able to address by stiffening the shocks (running 11 clicks from full firm all around for our bumpy tracks), but current setting works well everywhere else. Probably still something I should experiment with. The current tires really had me focused on it as they’re a bit taller than what I was running before.

If softer springs with stiffer damping will control travel better, I’ll be interested in hearing so. As I said, I may be looking at how to address all wrong, so please do let us know.
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      10-19-2020, 05:19 PM   #33
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Quote:
Originally Posted by bentom2 View Post
Maybe a poor choice of words on my part; I知 reaching the bump stops more than I壇 like, which depending on the tires I知 running, also means I get some pretty significant tire rub.

I might be able to address by stiffening the shocks (running 11 clicks from full firm all around for our bumpy tracks), but current setting works well everywhere else. Probably still something I should experiment with. The current tires really had me focused on it as they池e a bit taller than what I was running before.

If softer springs with stiffer damping will control travel better, I値l be interested in hearing so. As I said, I may be looking at how to address all wrong, so please do let us know.
I would suggest measuring the rod length of the rear shock. You should have about 55mm including the bump stop when the car is on the ground.

I run a taller tire in the rear (295/35/18) and ride a lot of the curbs on the track and haven't had any issues with the suspension bottoming out / hitting the bump stops.

I even ran the rear shocks at 20 clicks soft to test and still didn't get to the bump stops on track.
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      10-19-2020, 05:54 PM   #34
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Quote:
Originally Posted by iBrakeLate View Post
I would suggest measuring the rod length of the rear shock. You should have about 55mm including the bump stop when the car is on the ground.

I run a taller tire in the rear (295/35/18) and ride a lot of the curbs on the track and haven't had any issues with the suspension bottoming out / hitting the bump stops.

I even ran the rear shocks at 20 clicks soft to test and still didn't get to the bump stops on track.
Thanks for the target measurement. I値l take a look.
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      10-20-2020, 10:15 AM   #35
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iBrakeLate - do you run this PBIR setup on other tracks? And have you tried a more uniform setup at PBIR? Something that can be used to rule out that the setup for some reason isn't playing nice with the car/suspension?

In the short video where you brake loose on the right turn exit of either 4, 5, or 6 (depending on which map you are looking at ) - does the track transition to off camber at that point? I can't exactly remember - but do think that you at least lose some banking in the track right there?

Can you possibly overlay the throttle telemetry on the videos? Not saying that is what happened - but could be useful just to rule out it was throttle related. It doesn't sound like it in the video, but sometimes video & audio might not sync perfectly.
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      10-20-2020, 10:55 AM   #36
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I have had Ohlins R&T on my 335is, they are great! Your "damping" settings sound like it is too soft, IMO. I don't know how bumpy the track is though, still feel the setting is too soft. Also, the R&T are all set at 7 - on all four corners, by default. It looks as if you might be treating the rear setting as a "2-way", taking out in order reduce rebound? Look at how soft you made the rear? The single-way adjustable coilovers need to be treated more equally on all four corners, I feel. As a starting point, I would try something like - Front 5 and Rear 6. That will definitely stiffen things up and make the rear much more solid! I got to the point with my Ohlins R&T that I was running 2 from max both front and rear on flat tracks in my 335is.
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      10-20-2020, 12:13 PM   #37
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Quote:
Originally Posted by OG Shark View Post
iBrakeLate - do you run this PBIR setup on other tracks? And have you tried a more uniform setup at PBIR? Something that can be used to rule out that the setup for some reason isn't playing nice with the car/suspension?

In the short video where you brake loose on the right turn exit of either 4, 5, or 6 (depending on which map you are looking at ) - does the track transition to off camber at that point? I can't exactly remember - but do think that you at least lose some banking in the track right there?

Can you possibly overlay the throttle telemetry on the videos? Not saying that is what happened - but could be useful just to rule out it was throttle related. It doesn't sound like it in the video, but sometimes video & audio might not sync perfectly.
I can overlay it, but we've already looked at the telemetry and it isn't the case.

Track doesn't go off camber.

Also this isn't just an issue with that corner, it just is more noticeable there as it is a longer sweeping corner.

Just received my softer springs, hopefully this solves the issue. If not, I will be removing the Ohlins from the car.

Again this is an issue only if the car is being really pushed to the limit of grip. If you drive it at 8/10s you don't notice it.
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      10-20-2020, 12:18 PM   #38
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Quote:
Originally Posted by M2joey View Post
I have had Ohlins R&T on my 335is, they are great! Your "damping" settings sound like it is too soft, IMO. I don't know how bumpy the track is though, still feel the setting is too soft. Also, the R&T are all set at 7 - on all four corners, by default. It looks as if you might be treating the rear setting as a "2-way", taking out in order reduce rebound? Look at how soft you made the rear? The single-way adjustable coilovers need to be treated more equally on all four corners, I feel. As a starting point, I would try something like - Front 5 and Rear 6. That will definitely stiffen things up and make the rear much more solid! I got to the point with my Ohlins R&T that I was running 2 from max both front and rear on flat tracks in my 335is.
I appreciate your input, but you are talking about a different chassis here. We've tried everything. So when we talk clicks, we always talk from full stiff back to full soft. 0 being fully stiff and 20 being fully soft.

I've tried 7 all around, 12 all round, and 20 in the rear with 12 in front. Nothing really helped hugely with this issue.

The biggest change in positive handling characteristics was when the rear shock length was adjusted to the correct 55/45 compression to droop ratio.

The car with these spring rates are so stiff that can't even touch a single curb on track, or the car literally gets thrown off the curbs.

The last theory is that the setup is extremely over sprung. Which if you look around no other big name manufacturer provides their setup with such high spring rates.

Going to install the new springs when I get a chance and give it a try again.
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      10-20-2020, 01:08 PM   #39
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Quote:
Originally Posted by iBrakeLate View Post
I can overlay it, but we've already looked at the telemetry and it isn't the case.

Track doesn't go off camber.

Also this isn't just an issue with that corner, it just is more noticeable there as it is a longer sweeping corner.

Just received my softer springs, hopefully this solves the issue. If not, I will be removing the Ohlins from the car.

Again this is an issue only if the car is being really pushed to the limit of grip. If you drive it at 8/10s you don't notice it.
Hopefully the springs fix it for you. I run the Ohlins R&T as well with their suggested spring rates & haven't seen this kind of issue when pushing hard - but we all certainly have different driving styles & prefer different setups so hopefully the softer springs do the trick. I hope there is not an underlying issue with the dampers besides what you have already looked into - that's why I was asking about all the other stuff just to rule things out.

Good luck with the springs
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      10-20-2020, 11:18 PM   #40
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What alignment settings did you go with for the revised set-up ?
Have you looked onto some race (helm jointed) style toe-links ?
I used the standard spring rates Ohlin supplies..no issues / problem on track.
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      10-21-2020, 03:32 AM   #41
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I would make sure they are within the valving range of your R&T... 70 in the front is probably OK, but going down to 120 from 190 will most likely be outside of the valving range. Speaking from personal experience, I also found the original R&T setup to be on the soft side as I tracked with the original setup for a year and decided to revalve them to 120/220. Regarding the rear sitting on the bumpstop, R&T is rebound biased so there isn't much compression damping to begin with, and the adjustments mostly account for the low-speed damper movements. I don't believe going with a much softer rear spring would alleviate this issue at all.
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      11-10-2020, 05:05 AM   #42
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How old are your tires? I suggest you try with a set of tires that arent heat cycled.

I run into that problem on my car

Spring rate also will be drastically different with a true coilover if that is the benchmark you are comparing against. Ohlins is not a true coilover in the rear.
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      11-10-2020, 09:37 AM   #43
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Quote:
Originally Posted by iBrakeLate View Post
I appreciate your input, but you are talking about a different chassis here. We've tried everything. So when we talk clicks, we always talk from full stiff back to full soft. 0 being fully stiff and 20 being fully soft.

I've tried 7 all around, 12 all round, and 20 in the rear with 12 in front. Nothing really helped hugely with this issue.

The biggest change in positive handling characteristics was when the rear shock length was adjusted to the correct 55/45 compression to droop ratio.

The car with these spring rates are so stiff that can't even touch a single curb on track, or the car literally gets thrown off the curbs.

The last theory is that the setup is extremely over sprung. Which if you look around no other big name manufacturer provides their setup with such high spring rates.

Going to install the new springs when I get a chance and give it a try again.
It am very interested in hearing your feedback, what you are saying makes prefect sense. I always try to talk people out of stiffer springs, in general. They tend to hurt overall performance more than help. This also seems to be the general consensus from vendors, manufactures, etc.

Edit: I am also curious as to what you hot tire temps are after 5 laps? With RE71-Rs it seems your optimal grip arrives around lap 4 to 6, track, temp, etc. depending. You might want to remove 3 psi from the rear only as a test. Without knowing the hot temps though, maybe more, maybe less. For RE71s it seems 33-35 hot is best, very hard to keep them in that range unless is a cooler day.
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      11-11-2020, 11:18 AM   #44
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I'd swear that video was out of my cockpit. I have EXACTLY the same issue.

I got my car out this weekend (Inde Motorsports Ranch in Willcox, AZ - new pavement, FUN track) for the first time since getting all the suspension installed and set up.

Present setup:
9.5 & 10.5 x 19 Apex EC-7 wheels
Toyo R888R sneakers - 265 & 295 running 36-37 hot
RSR cage
Pagid Yellows (this is changing next round)
Ground Control camber plates (noisy things) and Turner adjustable rear toe arms
ヨlins R&T suspension both front and rear are 10 clicks out (will play with these next round)
Ride height is 8 mm lower than stock (supposed to be 10mm lower). There was an intentional reason for the higher setting that's been addressed (trailer setup).
Car is set at 3 degrees camber, zero toe front
1.9 camber, presently mentally blank on toe in - 1 degree, I believe.

Manners are fantastic right up to starting to add throttle after apex and the back end gets twitchy, often leading to nice high speed drifting (can be fun, can make one's butt pucker).

It's quite consistent left or right handers and as the OP stated, the faster, more open sweepers seem to be more problematic than the tighter stuff.

I'll take the steps OP has as far as preload and ride height (I'm sitting too high - definitely in the rear) and see what happens next month at a smaller, tighter track (Wild Horse Pass - Bondurant course).

I really hope I can dial it in w/o going to a softer spring rate. I do agree that they seem to be pretty stiff the way ヨhlins sets them up.

Other than this, the car is brilliant to drive on the track.
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