Spacer effect and sideeffect question

Good question! I am thinking about doing the same. How about spacers at the front and the back? They give the car a wider look!

Ton

 

I believe you need to take into account the wheel offset width and the spacer thickness and compare that to the stock condition, to consider any possible performance difference relative with the stock condition.

However, assuming you were merely taking the stock wheels with stock size/width tires and installing longer lug bolts with a 25mm (1 inch) spacers to widen the track at all four corners, I believe that there would be no noticeable effect on understeer/oversteer.

Altering the car's understeer/oversteer at the limit of adhesion really comes from changing the size of the front tire contact patch relative to the rear tire contact patch. Proportionally more front tire contact patch allows the front to grip better relative to the rear reducing understeer, and increasing oversteer (since the rear now grips worse relative to the front).

Hope this helps.

Kind Regards, Chris

 

A) you will decrease rear end cornering stiffness
B) you will increase reaar end grip
C) you will increase the axle bearing loads
D) you will increase the suspension bushing loads
E) you will promote UNDERsteer

 

A) decreasing rear end cornering stiffness means that the car will roll more in the turns at the same cornering load, this is a consequence of the suspension geometry and the increase in track. Effectively, the wider track has a bigger lever to compress the spring at that corner. So, with the same amount of weight transfer, more roll results. The effect is small unless the new tires are a lot more grippy than the old tires.

C) no, not without a F1-like cost structure--wait for them to wear out

D) no, not without a F1-like cost structure--wait for them to wear out

 

The effect of increasing the track on suspension stiffness is much less than you might think. With a twin A-arm suspension the wheel moves up and down with only a few degrees of roll and most of it is at the top of the suspension travel. The instant is about 3 feet away from the wheel, so the reduction in stiffness is about 1.5/36 x 100 or about 4%. Something, but not much.

 

I don't think the wear will be excessive. A spring, ride hieght, or roll bar change will get any handling problem corrected. The problem is getting the tire inside the fender. You would need to flare the fenders as far as I can tell. You might get 360 fronts inside the rear fender, but they are pretty narrow and may still hit the fender. I think the best bet would be to back date the suspension. I'm not sure what parts need to change, you'd need to check the parts book, but 360 wheels will fit on the earlier cars if aftermarket springs are fitted (you need about 4% stiffer springs anyway).

Remember this link, they look right at home in these fenders
http://www.berlinettamotorcars.com/GTOstylebodyparts.htm

 

The answer realy depends a lot on the tires you have. I have seen several posts about 25mm spacers, so I guess that is possible with stock size/profile tires and stock ride hieght. My car is lowered a littte more than .5", it has 285/35-18 tires, and the face of the wheel is about .5" further out then stock and it works....just. The reason the wheel has to be inside the fender is that the tire need some place to go when you hit a bump, it goes up into the wheel well. It need to be able to move up about 3" from the normal ride position. If you push the wheel out to the edge, and put on a wide low prfile tire, it will hit the fender when ever you hit a bump. You don't nee to push the wheels out to make a big differance in the way it looks, I personally think mine would start to look silly if the wheel went much further out.

 

I think that if you took a brand new car and did nothin to ti, the suspension bushings and wheel bearings will last at least 100K miles.

I also think that if you took a brand new car and put wheel spacers on it and drove it just like a completely stock car, you would get 85K miles on the wheel bearings and suspensions bushings.

So, the increase in wear rate is "not that great", but it is still there. However, if you go out and track the car, you may decrease the life of these parts a lot more than the above indicates.

 

Mitch,

Do you really think 15% decrease in life of the bearings? I know it would be a huge amount of math to work out an actual figure but I was just thinking about the 348 Speciale and late USA Spiders that have the extra 25mm on the mounting face of on the rear wheels (I suppose this is the same as putting 25mm spacers on a standard set of 348 rear rims) – Are the rear bearings up-rated on these cars to allow for the added track width increase?
15% seems a lot to me, but as you say if you were to track the car the stresses are much greater that normal road usage.

Cheers

Paul

(Omar - Just about to reply to your other thread!)

 

with a one inch (25 mm) increase in track, per side, two inches total, one reduces maximum load transfer, on that axle, relative to what it was originally. Theoretically, now you've shifted the roll-couple distribution forward. This, theoretically, is a shift toward understeer. Did I mention the word "theoretical"?

However, for all intents and purposes, for a primarily street driven car, you've accomplished a cosmetic change only. There are more significant hardware characteristics and dynamic parameters that influence handling than this two inch track change on this Ferrari.

As for wheel bearing life, if the modification uses proper lug studs/bolts with proper thread engagement, and it looks good, I wouldn't worry about it. We're talking about a road car, not race car, right?

Best regards,

Rob Schermerhorn

Ps, the topic header "sideeffect" reminds me of roundy-rounders talking about increasing "side bite" in the corners