Switched from RCE Yellows to Bilstein B8/RCE Tarmac Springs

[was385]

Originally Posted by Gliderx

Sooooo are you going to sell your yellows?? I'm in the market for them haha

I will be selling. Trying to find someone local because shipping springs is expensive and a pain with my work schedule.

[was385]

Originally Posted by SomeoneWhoIsntMe

you're not opening the strut it's self, just an outer casing that they put over the strut shaft so it can bolt to the knuckle and be inverted.

I'd rather not tamper but having this information is still helpful to the discussion for anyone evaluating their options.

[Ubersuber]

Originally Posted by SomeoneWhoIsntMe

It's not that hard to pop those open and trim the bumpstops inside the inverted housing, is it?

Depends. The rear dampers aren't inverted and neither are the front struts. Inverted dampers would have the damping oil inside the exposed "piston" rod allowing for a much smaller diameter actual piston rod. There would be no point to building these for the rear as the rear dampers are not loaded, all suspension loads are taken by the links, but the rear springs are preloaded I believe, though possibly not by much.

Bilstein builds inverted front struts which are of course loaded suspension components, and these have slightly lower unsprung weight and much better rigidity in their function as the steering "knuckle" since what would normally be the piston rod on a strut is the cylinder that contains the damping mechanism, oil and gas. The strut body where these gubbins are normally located is just a sturdy dust shield for the piston rod which in turn can be much smaller diameter than a regular strut would require.

Monotube dampers can be installed wither way up and could care less. There should be a dust shield when installed either way up.

The way Subaru builds the rear suspension the damper and spring are essentially a coilover unit which unbolts as such. To trim the bump stop without risking nicking the piston rod you should use a spring compressor to dismantle the coilover and to reassemble it. The bump stop cannot be accessed with the dust cover in place and the dust cover is retained by the upper spring plate, corresponding to the upper strut plate on the front.

[vroom4]

Originally Posted by sluflyer06

I couldn't agree less, I'm running toe out up front on car and was expecting to find high speed wandering, etc. But zero instability or wandering at highway speeds and higher.

The car is miserable to drive with toe out. Im at just under 1/4" total toe out front and 0 toe rear...after long trips my wrists hurt from doing small corrections to keep the car in the lane.

[Ubersuber]

Originally Posted by sluflyer06

I couldn't agree less, I'm running toe out up front on car and was expecting to find high speed wandering, etc. But zero instability or wandering at highway speeds and higher.

Depends if dynamic toe is still negative when you drive. If you have enough toe out that the front wheels toe out under dynamic loads you sure will feel the wander under braking at least. If you have a lot of toe out you will get wander even if you aren't braking.

Toe out is an interesting setting. It can work on a twisty track but can get hairy when braking at high speeds as you enter the bend.

[SomeoneWhoIsntMe]

Originally Posted by Ubersuber

Depends. The rear dampers aren't inverted and neither are the front struts. Inverted dampers would have the damping oil inside the exposed "piston" rod allowing for a much smaller diameter actual piston rod. There would be no point to building these for the rear as the rear dampers are not loaded, all suspension loads are taken by the links, but the rear springs are preloaded I believe, though possibly not by much.

Bilstein builds inverted front struts which are of course loaded suspension components, and these have slightly lower unsprung weight and much better rigidity in their function as the steering "knuckle" since what would normally be the piston rod on a strut is the cylinder that contains the damping mechanism, oil and gas. The strut body where these gubbins are normally located is just a sturdy dust shield for the piston rod which in turn can be much smaller diameter than a regular strut would require.

Monotube dampers can be installed wither way up and could care less. There should be a dust shield when installed either way up.

The way Subaru builds the rear suspension the damper and spring are essentially a coilover unit which unbolts as such. To trim the bump stop without risking nicking the piston rod you should use a spring compressor to dismantle the coilover and to reassemble it. The bump stop cannot be accessed with the dust cover in place and the dust cover is retained by the upper spring plate, corresponding to the upper strut plate on the front.

We were talking about only the front bilstein B6/B8 struts. Because they're of an inverted monotube design, the bumpstops are internal. The specs from bilstein of each strut are identical except for the B8 has 1" shorter extended length, but Andy at RCE was speculating that the internal bumpstops in the B8 are probably shorter as well. I pointed out that it's not difficult to pop the housing open and trim that bumpstop, it's not an unheard of practice with the other inverted monotube bilstein applications.

How you went from that to trimming the stock rear bumpstops with the shock on the car I have no idea.

And for what it's worth, despite it being entirely irrelevant to the topic at hand, there's still an unsprung weight benefit to inverting a shock as long as packaging permits it.

[was385]

Originally Posted by vroom4

The car is miserable to drive with toe out. Im at just under 1/4" total toe out front and 0 toe rear...after long trips my wrists hurt from doing small corrections to keep the car in the lane.

That's a VERY different alignment setting than mine with twice the toe out up front and the lack of any toe in for the rear would contribute to less stability as well. I personally would not set my car up like that but at a more mild setup, I have no issues whatsoever.

[Ubersuber]

Originally Posted by SomeoneWhoIsntMe

We were talking about only the front bilstein B6/B8 struts. Because they're of an inverted monotube design, the bumpstops are internal. The specs from bilstein of each strut are identical except for the B8 has 1" shorter extended length, but Andy at RCE was speculating that the internal bumpstops in the B8 are probably shorter as well. I pointed out that it's not difficult to pop the housing open and trim that bumpstop, it's not an unheard of practice with the other inverted monotube bilstein applications.

How you went from that to trimming the stock rear bumpstops with the shock on the car I have no idea.

And for what it's worth, despite it being entirely irrelevant to the topic at hand, there's still an unsprung weight benefit to inverting a shock as long as packaging permits it.

I introduced the idea of shorter rear bump stops to this thread. Then somebody started talking about trimming the bump stops on the struts, which would not be a good idea unless you really understood what you were doing.

I trimmed my rears because all that can do is reduce rear roll spring rates which is safe even if it doesn't work. By "trimming" I actually cut 1/2 in out of the stiffest part as my objective was to change the point at which the bump stop was contacted without changing the spring rate rise curve too much. Trimming the soft end of the bump stop doesn't achieve that but instead increases the spring rate rise once the bump stop is contacted. When lowering springs are fitted this might not be a good solution, ideally you would want your spring supplier to also supply appropriate length and spring rate bump stops, as TRD does and I see you also do.

I also clarified what "inverted" means in this context because some posters seem to think it means simply upside down, which it doesn't in this context. It means the operating part of the strut is at the top, secured to the body and therefore sprung weight. Note that making a Bilstein shorter will change the unsprung weight by the weight of the shortened piston rod and that's all. The B6 will save only the difference between the smaller diameter piston rod and the weight of the oil chamber.

The common McPherson strut has the gubbins in the strut body and those gubbins are unsprung weight. Total strut weight is about the same but by inverting them can gain you a little unsprung weight saving, though not very much. The main advantage to inverted struts is the stiffness impossible to gain by other means, the strut itself being a load bearing suspension member combining the steering knuckle with the "virtual" upper wishbone (A arm).


Finally, I wanted people to know that cutting bump stops normally requires dismantling the coilover at the rear (and even more importantly the strut at the front) which should be done using a spring compressor. I expect the preload on the rear coilover isn't as high as it will be at the strut but either can be dangerous if you try to take them apart not realizing the spring has some preload.

[sluflyer06]

Originally Posted by vroom4

The car is miserable to drive with toe out. Im at just under 1/4" total toe out front and 0 toe rear...after long trips my wrists hurt from doing small corrections to keep the car in the lane.

That's way too much front toe out for street driving...big difference between the right amount and going overboard.

Originally Posted by Ubersuber

Depends if dynamic toe is still negative when you drive. If you have enough toe out that the front wheels toe out under dynamic loads you sure will feel the wander under braking at least. If you have a lot of toe out you will get wander even if you aren't braking.

Toe out is an interesting setting. It can work on a twisty track but can get hairy when braking at high speeds as you enter the bend.

Yes I agree, I was already aware of that and wanted to keep it reasonable enough to get stable braking which I have but still have more eagerness than a toe in setup.

[vroom4]

Originally Posted by sluflyer06

That's way too much front toe out for street driving...big difference between the right amount and going overboard.

The right amount of street drive is 0 or toe-in.

Autocross however, 0 toe and 1/8 toe out feel identical, so I went further and found the sweet spot.

[was385]

Originally Posted by vroom4

The right amount of street drive is 0 or toe-in.

Autocross however, 0 toe and 1/8 toe out feel identical, so I went further and found the sweet spot.

I think the point is that saying that toe out causes issues on the road because of your experiences isn't that relevant to most people as you have a fairly extreme setup in terms of toe out in the front and nothing to compensate in the back. Obviously everyone has to evaluate their own preferences but just for the sake of other people who might be reading this, the distinction is important.

[vroom4]

Ah yes, sorry for not reading careful enough, then I agree.

0 toe all around feels...decent, not good. Id say its a good middle ground for the once a month autocrosser.

[sluflyer06]

Originally Posted by vroom4

The right amount of street drive is 0 or toe-in.

Autocross however, 0 toe and 1/8 toe out feel identical, so I went further and found the sweet spot.

I don't dismiss the advantages of the alignment in the right environment, just pointing out for the general populace around here, that amount of *out* is not very stable as you pointed out.

[josealiceapr]

Thanks for the discussion. I am currently running on RCE yellows and stock struts - approximately 29k miles on the struts. Racecomp Engineering is such a valuable resource on these forums and have learned a ton from the knowledge he's shared on here.

I'm thinking about going the same route as in the original post, B8's with RCE Tarmac springs. My question is this (and I apologize if this has been discussed to death).

Are there any options out there for someone wanting to go stiffer on the spring rates than the option above without having to invest (not only $$ but time) in coilovers. My priorities are a quality suspension which maintains travel and correct geometry (no more than 0.75" drop).

Can any of the available struts (Bilstein, Koni, etc..) provide appropriate damping with a stiffer spring than the Tarmacs? If so, is a spring like that available? Would love to hear some thoughts on this.

Thanks