Q. How to cut down bump stops?

[2DoorJim]

Guys, I need (want) to lower the rear of my car. There is evidence of contact with the bump stops based on the clean area I see on them.

Years ago I recall simply cutting the top off the boob, but I'm wondering if there is a more eloquent method such as trimming the metal cup down in conjunction with cutting the rubber? Anybody have some feedback or ideas?

I'm using coilovers without integrated bumpstops so I'm relying only on the factory stops. My rear tires are a little tall hence the need to get the rear lower, got the 70s drag car thing going on.

[okayfine]

Can't cut the metal portion, as it has the dowel in it to stop it rotating when you go to tighten it. I have just trimmed some off the rubber. Remember that the motion ratio will also apply here, so if you trim 1/4" you gain 1" of travel. ...I think

[2DoorJim]

Wuz thinking of cutting a ring of metal from the top of the cup, so as to sustain an exposed amount of rubber, perhaps to give more compressibility. Not sure if this makes sense.

[okayfine]

I'd think it'd be tough to weld the trimmed cup back to the piece with the rubber. If you can keep the rubber happy, that would be more optimal than cutting the rubber then hoping you have enough during a big compression.

[bertvorgon]

For what it is worth...I took mine OUT! With the much shorter spring, but, with a rate that is almost impossible to blow through, I wanted no risk of sudden touch down on the bump rubber.

Previously, I had hacksawed off maybe 3/4", but, when the suspension touched down on it at Westwood...I was into the tire wall at 80 MPH>

[Three B's Racing]

For what it is worth...I took mine OUT! With the much shorter spring, but, with a rate that is almost impossible to blow through, I wanted no risk of sudden touch down on the bump rubber.

Previously, I had hacksawed off maybe 3/4", but, when the suspension touched down on it at Westwood...I was into the tire wall at 80 MPH>

I also removed my stops in `96 no issues here with the bumpy roads of NH, MA, CT, NY, NJ, PA, MD, WV when driving to Summit Point or anywhere else around New England.

[bertvorgon]

I figured that IF I hit the point that my springs coil bind.....I have more issues going on than just a big bump.

I have never bottomed my rear suspension, and that is on some stupidly fast drives with HUGE bumps and breaks in the pavement.

[2DoorJim]

Thanks for your replies guys. This gives me the idea to leave the stops out, set ride height then measure the amount of remaining travel.

I never looked to see what specifically interferes at full compression without the stops in place. I mounted a canister fuel filter which sits nearly above the right axle, might have to relocate it.

[2DoorJim]

So the bump stops are out and the rear has been lowered.

Measured at the axle centerline there is almost exactly 3" of compression travel until the tire contacts the inner fender/wheel house. At 3.5" the coil over is bottomed out. What are peoples thoughts on 3" of compression travel, sufficient?

Rear control arm angle is not favourable as it appears that I'm now on the wrong side of the curve, so I added a little extra toe in. Camber is at 2.5 degrees, which I presume is fine for semi sedate driving.

Chassis rake is 1/4" higher at the rear than the front (measured under rocker) considering going to 1/2" but curious what the consensus is on this?

I *discovered* my front fenders are in fact too close to the tires. The wheel opening was trimmed under full compression with the wheels turned, but something about the alternate direction I came off my driveway last week has resulted in the need to repair the left fender. I didn't get too worked up when it happened. Still testing new found vocabulary.

[okayfine]

Thoughts on 3" of compression - it's really going to depend on your spring rate, roads, and driving experience. Keith mentions he's got a stiff-enough rate that he's never stacked the coils. Fair enough. His experience will not necessarily match yours, depending.

On the rake, that's entirely a personal thing. My KA510 two-door was raked about 1/2" F/R and I thought it was grand. My SR510 white four-door was not raked and I thought it was perfect.

[bertvorgon]

I agree with OKFINE, 3" of travel is great, but, does that say you will actually use that in reality. If you did in my opinion it would say your springs are relatively soft. To have that is a very good safety margin for worse bump scenario. I would say I had close to 3" on the rear also, but, it has changed a bit over the rears

I have about 2 3/4" of travel up front, and only ONCE have I ever touched down on the small bump rubber left, and again that was on very high speed on a very winter worn road.

We/Specialty ran all the cars with a bit of rake, maybe 1/4" to 1/2" at most. Now, that being said, with my car right now is virtually dead level, as after 32 years my rear springs have sagged just a bit. I absolutely love the handling of my car right now, as the fore and aft weight transfer feels better than it ever did at least on race slicks.

Car looks great!

[okayfine]

Car looks great!

Yeah, I forgot to comment - car looks fab!

[2DoorJim]

Thanks for your compliments guys. You might recall a time in my build thread where I was apprehensive about going forward with the body project as the current trend is retro (though I was after retro 80s). I'm stoked by people's reactions so far though my audience has been the general car community and not the hard core 510 crowd, so it's nice to hear your positive feedback.

I went for a quick burn last night then pulled in and took measurements to see where it settled. Generally my alignment is where I want it, I think, so I'll put it on scales now and corner balance it.

I only got about 600 miles on it last fall before I put it away for winter and last night is only the second time the engine has fired this season. One issue surfaces each time I drive it, and that's tracking of ruts.

This takes me back to when I was young and recall this issue when going to wide tires. Appears nothing has changed.... do you guys have any advice to help mitigate the issue?

There's no issue driving on good roads but older well worn asphalt is annoying. A friend stopped by and mentioned that I'd see an improvement going to non-R compound tires but I'm wondering if there are any tweaks which might help, though I doubt there is a cure.

My other early wide tired 70s toys aren't really bothered by ruts so I'm not sure what gives.

[Byron510]

I have the same issue with R compounds on the Bronze, run 7", zero offset rims. I dialed in 5 degrees of caster hoping it would go away - it was better but still not good. I did switch up to Yoko S drive tires and there was a marked improvement, but it still tracks rutts. Jeff believes I also have a steering arm issue, and he's been working on some modeling for me. Aside from Street tires and giving up some stick, I can't advise further. Now I just carry my R compounds to the track for track days, and I change them at home and drive to solo events that are local.

Byron

[2DoorJim]

Byron I bought these bridgestone R compounds only because they offered the sizes I wanted and the only other selection was non grooved Hoosiers and such. I'd have preferred a high performance summer tires so based on your feedback I'm going shopping again to see if any other brands have surfaced with a new run.

I'll also look at reducing castor like you did. There is no track here anymore and my street driving is not aggressive.

Thanks for your feedback.