Standard Suspension Bump Travel

[86•BRZ]

Originally Posted by Suberman

really? I've got to check this out, it would explain the weird handling quite nicely. Oversteer arrives at ridiculously low cornering loads. I've never experienced a car which hits its bump stops in normal driving.

This was my initial thought. Hence my confusion.

[Racecomp Engineering]

Originally Posted by mike156

Many cars use bumpstops as a second spring now (many put the car on the bumpstop at normal ride height even). It lets them use a soft spring for normal driving then the spring package goes very progressive over larger bumps. Modern springs are wound in a manner to offset the bending load put on the strut. I wouldn't be surprised if the bumpstop approach is a way to keep strut friction down, along with soft ride rates, but then the ability to soak up big stuff.

YEP ! And to add to it....

Porsche, BMW and Mercedes have done this for over 30 years, especially in their low gas, twin tube use. They design in TONS of droop travel but little bump travel and instead use the progressive bump rubber to pick up where the spring left off. For an OEM car this works well. LArge sways, progressive bump rubber and tons of droop means a LARGE pothole doesnt disrupt the car(or the occupants).

Take that same car and lower it? ....and NOW a nice mid corner bump turns into a mid corner DITCH/ JERSEY BARRIER/ CAR NEXT TO YOU fender !

Myles Williams
RCE since 2003

[autobrz]

the stock car is pretty jarring over dips though... the rear feels like it bounces when going over dips, although the stock car does seem to have a ton of grip despite the lack of bump travel... very confusing...

[Wepeel]

Hmm. Well now this really has me thinking about the potential to tune bumpstops for stock-class autocrossing. I didn't realize the bump stops were that close to being engaged at rest. And I wonder how much ride height (if any) you lose going to a no-gas-pressure koni.

[bfrank1972]

Originally Posted by Racecomp Engineering

YEP ! And to add to it....

Porsche, BMW and Mercedes have done this for over 30 years, especially in their low gas, twin tube use. They design in TONS of droop travel but little bump travel and instead use the progressive bump rubber to pick up where the spring left off. For an OEM car this works well. LArge sways, progressive bump rubber and tons of droop means a LARGE pothole doesnt disrupt the car(or the occupants).

Take that same car and lower it? ....and NOW a nice mid corner bump turns into a mid corner DITCH/ JERSEY BARRIER/ CAR NEXT TO YOU fender !

Myles Williams
RCE since 2003

And yet you guys sell lowering springs So basically the only solution to lower these cars and have any real suspension travel at all is to go coilovers?


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[Racecomp Engineering]

Originally Posted by bfrank1972

And yet you guys sell lowering springs So basically the only solution to lower these cars and have any real suspension travel at all is to go coilovers?


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We sell our lowering springs with a very mild drop (less than an inch) and we include replacement bumpstops front and rear. We wouldn't do it any other way.

Yes to get a lot of travel you need coilovers.

- Andy

[Racecomp Engineering]

Originally Posted by Suberman

really? I've got to check this out, it would explain the weird handling quite nicely. Oversteer arrives at ridiculously low cornering loads. I've never experienced a car which hits its bump stops in normal driving.

Remember they are very progressive, so you don't necessarily feel it "hit." You've almost certainly been in a car that uses the bumpers normally.

I'm really curious of OEMs do it so they can have firmer rates via the bumpstops but still don't need to use much rebound damping and can keep crappy shocks on the car, among the other reasons speculated above.

- Andy

[Racecomp Engineering]

Originally Posted by Wepeel

Hmm. Well now this really has me thinking about the potential to tune bumpstops for stock-class autocrossing. I didn't realize the bump stops were that close to being engaged at rest. And I wonder how much ride height (if any) you lose going to a no-gas-pressure koni.

MINI guys do it and I'm sure others do too.

- Andy

[bfrank1972]

Originally Posted by Racecomp Engineering

MINI guys do it and I'm sure others do too.

- Andy

I think the original mini classic suspensions were rubber cones - sounds like glorified bump stops to me

[Racecomp Engineering]

Originally Posted by bfrank1972

I think the original mini classic suspensions were rubber cones - sounds like glorified bump stops to me

Exactly! That car too.

- Andy

[Racecomp Engineering]

Originally Posted by bfrank1972

And yet you guys sell lowering springs So basically the only solution to lower these cars and have any real suspension travel at all is to go coilovers?


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to be super CLEAR…our bump stops are MUCH shorter and firmer ( progressive 3 stage) than stock. So you gain travel technically. Not to mention the spring RATE is increased and there is less travel USED in most situations.

Small detail many forget.

NOTE: not said in a defensive way, just trying to explain better !

Myles

[bfrank1972]

Originally Posted by Racecomp Engineering

to be super CLEAR…our bump stops are MUCH shorter and firmer ( progressive 3 stage) than stock. So you gain travel technically. Not to mention the spring RATE is increased and there is less travel USED in most situations.

Small detail many forget.

NOTE: not said in a defensive way, just trying to explain better !

Myles

Hey just FYI my statement wasn't accusatory - this thread regarding bump stop usage as part of the suspension has been pretty interesting and educational for me. I'm about to put sportlines on my car - yeah they're probably a bit too low for track usage (not gonna stop me!) but at least they come with different bump stops.

Hummm maybe you should market a new line of performance progressive rate bump stops!

[Suberman]

Originally Posted by bfrank1972

I think the original mini classic suspensions were rubber cones - sounds like glorified bump stops to me

Well, Hydrolastic suspension was a tad more sophisticated than that.

The original rubber cone springs didn't survive market opinion for long.

[Suberman]

So I'm looking at pictures of this suspension and I don't see any bump stops. There have to be some. Are these inside the shock bellows?

I do see a toe control link that has me suspicious that rear toe is manipulated through the compression arc to induce the oversteer I am experiencing during sharp turns.

That toe link makes the lower "wishbone" into a parallel arm setup, but I'm sure the travel arc of the toe control arm is shorter than that of the main transverse link. The outside rear wheel will toe in under compression while the inside rear wheel will toe out under droop if this is in fact the case.

I'm looking at Edmunds walk around here:

http://www.edmunds.com/car-reviews/t...alkaround.html