[John Stimson]

The Elise has 5 possible height settings on the stock shocks. It would be legal to use a lower or higher setting, if the factory service manual has instructions for changing the setting.

Has anyone looked in the FSM for such a procedure? Is it in there?

If it's allowed, then you can lower the car. But you'll hit the bumpstops sooner. That's probably a bad thing, but there are some people who have set up their stock suspensions to continuously ride on the bump stops and use them as the springs. The one I heard about was on a Neon, which doesn't have nearly as finely-tuned suspension as the Elise. So let's assume we want to avoid riding the bump stops.

The shock rules say that the overall extended length must be within 1" of the stock shocks. The length of the body plus the length of the bump stop must not be longer than with the stock hardware...you are allowed to change the bumpstop or have a shorter shock body to make this true.

So if you are allowed to lower the spring perches, then you can compensate for reduced bump travel by cutting the bump stops and/or using a shorter-bodied shock.

You can't make the shock body a lot shorter. You are limited by the fact that the extended length can only be 1" shorter...that means that if the body is 1" shorter, the shaft is not shorter...and the piston would collide with the bottom of the tube at the same compressed length. Someone who wanted to play this game would have to determine how close the piston comes to bottoming out with the stock bump stop, in order to know how much to shorten each part (the body, bumpstop, and shaft) in order te retain the most travel in each direction.

Alternately, the lower spring perches (if it's legal to use them) could be used to compensate for the increased ride height from using very high gas pressure in the shocks. High gas pressure can be used to augment the coil springs and provide a higher total spring rate.

 

[CrashTestDummy]

if 'we' are hitting the bump stops why cant you just cut them? I dont think there is anything in the rules stating they cant be altered.

I could be wrong.

 

[John Stimson]

I said you can cut the bump stops.

But it might not be the best solution. First, the transition from soft to hard spring rate when you hit the bump stop becomes more abrupt when you cut the bump stop. Second, if you cut off too much, you might not be left with enough material to protect the piston from bottoming in the tube, or to cushion the impact of the shock tube on the "hat".

I think that the more bump stop you can leave in place, the better...make the rod and the body as short as possible within the rules and physical constraints, then trim the bump stop as necessary.

I think it's a moot point unless it's legal to change perch settings. There should be enough travel at the stock height for a good set of shocks to keep you off the stops.

 

[del105]

it would be perfectly legal to use shims to adjust spring perch height. My question to you is why? I'm just curious what is the car dong that you don't like. I haven't gotten my car yet, but from my experience most car shocks are way under damped for auto-x and need to be replaced. with an adjustable shock. I personnally would go that route before I tried using the bump stops as a shock.

 

[John Stimson]

I don't know where you got the idea that I think that the bump stops could be used as shocks.

My main point is the possibility of lowering the car using the factory-provided height settings. I mentioned the bump stops because if you lower the car without doing anything else, you're going to hit the bump stops more frequently which is a bad thing. I suggested the possibility of changing the shock dimensions and the bump stops as a legal way of avoiding hitting the bump stops.

I don't have my car yet either; I'm just throwing out ideas for people to think about. Being able to lower the car in Stock category seems like it would be a good thing.

Adjusting the perch height with shims is absolutely not legal. You can use shims to achieve the stock perch height, if you have non-stock shocks with non-stock perch heights. I'm talking about using the 5 different snap-ring grooves in the shock body that allow you to position the spring perches at 5 different heights. That is only legal if the shop manual describes their use. If it doesn't, you can't use them even though they are there.

 

[del105]

yeah, I guess I didn't read the whole thing. Adjustable spring perches are allowed, but the spring load bearing surface must be in the same location relative to the shock mounting point as on the standard part. Shims may be used to achieve compliance. I'm still not understanding why.

I'm no suspension expert, I'm trying to learn more.

What will this do? "I'm talking about using the 5 different snap-ring grooves in the shock body that allow you to position the spring perches at 5 different heights. That is only legal if the shop manual describes their use. If it doesn't, you can't use them even though they are there"

 

[John Stimson]

Oh, okay. Let me address the two questions separately.

The shims are allowed, in case your perches are not continuously adjustable (threaded) and the aftermarket perches are slightly lower than stock. You use the shims to match the stock height.

The shocks on the Elise aren't threaded. The spring perch slides down and sits on a snapring, which is seated in a groove around the body. The snapring supports the weight of the car -- it's impressive if you think about it. There are 5 grooves, spaced 5mm apart. You can move the snapring to another groove to change the height of the perch.

On some cars, like certain Porsches, the stock suspension is adjustable for height, and the adjustment procedure is described in the service manual. Therefore those cars can be raised, lowered, cross-balanced, etc. According to the Solo rules, it's not just the presence of the adjustment mechanism that makes adjustment permissible. It has to be "specified by the factory as a normal method of adjustment".

 

[apkom]

How about making it higher?

On the same note would lifting LSS car to non-LSS heght to avoid scraping be stock legal. Will it mess up handling?

 

[Evl]

According to the Solo rules, it's not just the presence of the adjustment mechanism that makes adjustment permissible. It has to be "specified by the factory as a normal method of adjustment".

It does not say that it has to be specified by the factory in the service manual. Could this be interpreted to mean that the brochure listing ride height adjustment in the LSS pack indicates that the factory considers this normal adjustment? Or more to the point, is the SCCA likely to interpret it that way?

 

[RopaS2]

It does not say that it has to be specified by the factory in the service manual. Could this be interpreted to mean that the brochure listing ride height adjustment in the LSS pack indicates that the factory considers this normal adjustment? Or more to the point, is the SCCA likely to interpret it that way?

Here's the rule:

13.8 "Both the front and rear suspension may be adjusted through their designed range of adjustment by use of factory adjustment arrangements or by taking advantage of inherent manufacturing tolerances. This encompasses both alignment and ride height parameters, if such adjustments are provided by the stock components and specified by the factory as normal methods of adjustment."
If Lotus lists ride height adjustability for road use, then it's allowed. If, OTOH, the brochure said something like, "Ride height is adjustable for off-road or competition use," then it would not be allowed.