As the topic sums up.. Can you have different sized wheel spacers on the front and rear of the evos.. particularly evo x? without any adverse reactions effects?

I.e. 25mm rear and 20mm front?

Thanks?

 

it's complicated, on an AWD car, the wheel sizes need to be the same due to the diffs but wheel spacers may be different. To be safe, i would run 20mm all around

 

Where do people get these random numbers from.....

Since you've given a general recommendation, let's say I've got 11 inch wheels with a +0 offset, yes I'll run +20 mm spacers all around.....

 

Yes, there have been a few people who've run the same size wheels, but different offsets front and back. I'd wait for Iowa to chime in, he'd know the answer in detail.

 

Iowa despises offset discussions and tries his best to steer clear of them entirely.

We need some kind of calculator or something

 

I think Iowa despises questions in general.

Very informative though when he does comment.

 

I have no problem with offset questions, in general, although I can't imagine a new question ever being asked. The issue of whether offsets need to be the same, front and rear, has been addressed many times; the answer is that they don't have to match.

ps. I only despise the idea that there are no stupid questions, as it is demonstrably wrong

pps. the idea that 20mm all around is safer than, say, 15mm at one end and 20mm at the other end is also demonstrably wrong

 

I thought wider track front to rear could help with turn in understeer. Seems a lot of autocross guys use wider front spacers.

 

You see lower offsets in the front on autocross cars for several reasons. First, if the rules allow you to run any offset you wish, but don't allow body work, then you usually end up being able to go with a lower front offset (to maximize track) because the fenders cause less grief in the front. Second, a lower front offset is often required to keep the inside edge of the wheel and/or tire off the suspension. Third, some folks are so accurate in their car control, that a higher rear offset is needed to keep the inside rear wheel from clipping cones.

It may also have something to do with changing the dynamics, but I don't see how it would be at turn-in. I'm not saying that it can't affect turn-in; just that I don't see how it could.

 

http://www.sccaforums.com/forums/aft/37389/afpg/3

The vorshlag test evo ran into some offset issues in this thread relating to scrub radius. Check it out.

 

I wish I understood why they said that a solution for excess scrub is more caster. In general, more caster with a high scrub radius means more jacking when turning.

 

There are a few odd things in that article. One of which was the poor performance of the front with large offset rims, and the second being worse performance after moving to ast 5200's from 4200's.

one reason i suspect they assumed the scrub radius as the culprit is because with athe increased scrub radius from large offset / wide tires, it caused excessive roll center migration. As the steering angles increased, scrub radius decreased rapidly, causing a much more dramatic change in roll center. Perhaps with additional caster, the much larger arc the contact patch will make under high steering angle inputs will decrease the speed at which the roll center migrates per unit of steering input. Honestly i'm kinda talking out of my *** so let me know if this sounds reasonable.



The second odd thing in that article is that they noticed a loss of approximately .1 G of cornering force after moving to AST 5200's from 4200's. They changed a ton of variables simultaneously so its hard to identify for certain what caused what. Perhaps the ast 5200's valving favors compliance at higher track speeds whereas the 4200's have a priority for compliance at lower speeds? Again, i'm talking out of my *** here. Let me know if i'm completely full of it.

 

I have absolutely no idea what you're talking about.

 

it should be same...can't have differ size due to awd

 

Please take a few minutes and walk us through the logic behind this claim. I'm very curious to know why the offset has to be the same, front and rear, on an AWD car. Please use as many technical terms as possible, as I'll be passing your explanation along to Nissan and Bugatti, inter alia, as they currently sell AWDs with mismatching (front and rear) offsets and wheel-widths.

Thanks in advance and please ignore anyone who posts something along the lines of "it's a trap!" as that can't be related to this humble request.