Modifying Bilstein Shocks

[Kostamojen]

Originally Posted by Shankenstein

You took that way too literally and out of context.

We've been talking about removing part of the bumpstop not the entire thing.

[Racecomp Engineering]

Originally Posted by Kostamojen

I'd almost say it would be required for a 7" spring.

RCE, what do you think I should do... Lowering camber plates, shortening the bump stop, or both?

I wouldn't freak out about modifying the bumpstops. I did it on my own personal Mini Cooper with custom valved Bilstein fixed perch shocks. Not a huge deal but yes totally intimidating at first. I have not done it on their coilovers. I cut off a little of the soft and stiff section on my shocks. I don't know how long they are on your shocks but a little will go a long way.

That said, the RCE lowering camber plates would certainly make life easier (hey...TIC has some in stock right now!) but yeah that's not cheap.

I will say this...and it's not sales pitch I promise. The 400 lbs/inch custom valved Bilstein shocks I just rode on in a beast-mode supercharged BRZ were very comfortable. Baltimore City daily driveable. Exceeded my expectations. That car kicked ass and had a decent drop (30mm -ish). The firm spring rates help with the limited travel, but the valving has to work with the rates. My point is that the potential is there for a good all around set-up. It sounds like you're very close.

- Andrew

[Kostamojen]

Originally Posted by Racecomp Engineering

I wouldn't freak out about modifying the bumpstops. I did it on my own personal Mini Cooper with custom valved Bilstein fixed perch shocks. Not a huge deal but yes totally intimidating at first. I have not done it on their coilovers. I cut off a little of the soft and stiff section on my shocks. I don't know how long they are on your shocks but a little will go a long way.

That said, the RCE lowering camber plates would certainly make life easier (hey...TIC has some in stock right now!) but yeah that's not cheap.

I'm going to contact TIC about those, I think its time to move that direction anyhow. I might just do the bumpstops as well, but doing bumpstops alone doesn't increase the travel like those tophats will.

Should we be looking into roll center correction kits too? That worked wonders on my Impreza.

[Markiv]

Originally Posted by Racecomp Engineering

I will say this...and it's not sales pitch I promise. The 400 lbs/inch custom valved Bilstein shocks I just rode on in a beast-mode supercharged BRZ were very comfortable. Baltimore City daily driveable. Exceeded my expectations. That car kicked ass and had a decent drop (30mm -ish). The firm spring rates help with the limited travel, but the valving has to work with the rates. My point is that the potential is there for a good all around set-up. It sounds like you're very close.

- Andrew

Glad you liked my car I have had them on for a while and I agree, they are very comfortable and daily driveable given the roads around here.

[Dihudaxia]

Thanks for the replies on my question.

Seems that swapping out springs is not as simple as it looks!

[Racecomp Engineering]

Originally Posted by Markiv

Glad you liked my car I have had them on for a while and I agree, they are very comfortable and daily driveable given the roads around here.

Dude I totally blanked like an idiot when I walked back into the office and didn't say hi. For some reason it didn't occur to me that it was your car.

- Andrew

[AyJay]

I've been using a custom valved set of Bilstien PSS with 672 lb/in (12kg/mm) Swift springs (7" - 70mm ID) for years now on my S2000. The shocks and valve job are literally 6 years old now with years worth of track events on them and they still feel good as the day I bought them.

The revalve was done by the Bilstein Service Center down in SoCal. They were very good about recommending valving specs to the springs I wanted to run and the manner by which I would be using the shocks.


Edit: In the interest of full disclosure, I've only put about 20k miles in those 6 years since the rebuild. But those are some of the hardest 20k miles one could put since a several thousand of those miles represent back and forth to various tracks around NorCal and the track time that came with it.

[Kostamojen]

Originally Posted by Racecomp Engineering

That said, the RCE lowering camber plates would certainly make life easier (hey...TIC has some in stock right now!) but yeah that's not cheap.

TiC says they don't have BRZ ones in stock... I thought all Impreza snd BRZ front top hats were compatible still, or has that changed?

I mean I am running Impreza Group-N top hats right now!

[Hyper4mance2k]

[ame="https://www.youtube.com/watch?v=MHyVoiP0o_8"]Scion FR-S / Subaru BRZ | Comparing OE vs Bilstein vs FCM dampers, v2.38 - YouTube[/ame]

I'm shocked (pun intended) that Tein measured a difference between FRS & BRZ shocks, considering the cars share part numbers. I'm guessing their measurements could be attributed to variation in manufacturing, or a failure to test shocks from the same model year, considering the 2015 change from Showa to Sachs. Unless there's something I don't know...

Also, as per FCM's contestant recognition of the importance in considering motion ratios and cycles for flat ride, it continues to baffle me as to why people try to spring this car equal rates front & rear.The car in this video is basically running 5.8k F & 8.9k R

[Racecomp Engineering]

Originally Posted by Kostamojen

TiC says they don't have BRZ ones in stock... I thought all Impreza snd BRZ front top hats were compatible still, or has that changed?

I mean I am running Impreza Group-N top hats right now!

Shoot, my bad...they're GR Impreza tops which you don't want.

Originally Posted by Hyper4mance2k

Also, as per FCM's contestant recognition of the importance in considering motion ratios and cycles for flat ride, it continues to baffle me as to why people try to spring this car equal rates front & rear.The car in this video is basically running 5.8k F & 8.9k R

Flat ride is important for comfort on passenger cars with very low spring frequencies and damping ratios.

Real motorsports engineers don't give too much of a shit about flat ride. There I said it. lol. I've heard that from TONS of engineers that are "in the business."

OptimumG for example:

The above theory was originally developed for passenger cars, where comfort takes priority over performance, which leads to low damping ratios, and minimum pitching over bumps. Racecars in general run higher damping ratios, and have a much smaller concern for comfort, leading to some racecars using higher front ride frequencies. The higher damping ratios will reduce the amount of oscillation resultant from road bumps, in return reducing the need for a flat ride. Damping ratios will be explained in the next tech tip in detail. A higher front ride frequency in a racecar allows faster transient response at corner entry, less ride height variation on the front (the aerodynamics are usually more pitch sensitive on the front of the car) and allows for better rear wheel traction (for rear wheel drive cars) on corner exit. The ride frequency split should be chosen based on which is more important on the car you are racing, the track surface, the speed, pitch sensitivity, etc.

It's a starting point to be looked at before load transfer calculations, simulations, testing, etc.

There is no magic formula for setting up a vehicle. Your rear wheel drive car shouldn't be tuned the same as a front wheel drive or all wheel drive car or a car with double wishbones all around, etc. The specific rates you mentioned may work well on a BRZ with no rear bar and a large front swaybar. That has it's own compromises.

- Andrew

[Hyper4mance2k]

Originally Posted by Racecomp Engineering

There is no magic formula for setting up a vehicle. Your rear wheel drive car shouldn't be tuned the same as a front wheel drive or all wheel drive car or a car with double wishbones all around, etc. The specific rates you mentioned may work well on a BRZ with no rear bar and a large front swaybar. That has it's own compromises.

- Andrew

I totally agree with this. FCM has some interesting opinions on swaybars in his setups. And, as is always said, everything is always a compromise somewhere unless it's being purpose built. People in Japan & Germany have the benefit of governments that spend significant amounts of money on infrustructure that lets car guys enjoy not needing to make such great compromises for street drivability. I also think that car was specifically being setup for autoX, which takes into account places like Petco Park and 405 driving. The freeways out here are like glass compared to SoCal, but the surface streets are a nightmare in comparison. Compromises everywhere. If you've ever driven the 405S in LA you realize how damn important flat ride can be. A stock twin at speed on the 405 feels like the street is paved with ruffles.

[Racecomp Engineering]

Originally Posted by Hyper4mance2k

I totally agree with this. FCM has some interesting opinions on swaybars in his setups. And,, as is always said, everything is always a compromise somewhere unless it's being purpose built. People in Japan & Germany have the benefit of governments that spend significant amounts of money on infrustructure that lets car guys enjoy not needing to make such great compromises for street drivability. I also think that car was specifically being setup for autoX, which takes into account places like Petco Park and 405 driving. The freeways out here are like glass compared to SoCal, but the surface streets are a nightmare in comparison. Compromises everywhere. If you've ever driven the 405S in LA you realize how damn important flat ride can be. A stock twin at speed on the 405 feels like the street is paved with ruffles.

I agree with a lot of what FCM says and generally like his tuning philosophy.

I loled at "paved with ruffles". That sounds about right.

Baltimore city is a just a car destroyer. Most of our highways aren't terrible, but regular streets even in the nice suburbs can be miserable.

- Andrew

[Hyper4mance2k]

Originally Posted by Racecomp Engineering

I agree with a lot of what FCM says and generally like his tuning philosophy.

I loled at "paved with ruffles". That sounds about right.

Baltimore city is a just a car destroyer. Most of our highways aren't terrible, but regular streets even in the nice suburbs can be miserable.

- Andrew

Yeah. I'm living in MD now. I've pretty much experienced everything the US roads have to offer... The 40 westbound an hour or so out of Oklahoma city is a lesson in how to not pave an interstate highway. The concrete slabs are cupped like Pringles. (MMmmmmmm Sour Cream & Onion Pringles )

[Kostamojen]

FYI I'm getting an occasional loud "ping" from the front springs, like they are popping back into place or something. Usually when going over speed bumps/curbings (round curb on my driveway) and sometimes when turning. It only happens once though and stops... I'm thinking the springs are too low now and they aren't compressed at all when at full droop?