Tire to fender clearance

[nuisance]

With the R model, we have moved the suspension up 13/16" or so relative to the frame. We have not moved the body relative to the frame, so the tire to body clearance is reduced by 13/16", which would imply a tire outside diameter 1 5/8" smaller to fit relative to the S. The S max size recommended is 215-40/17, or 24" diameter.

Many of the S model builders have experienced fender rubbing problems with what seem like puny tire sizes. I am having problems fitting what seem like small race tires (225-40/17) under the fenders, and spacers are not helping.

Any of you guys with running R models found a solution other than 15" wheels?

I have thought of putting a spacer in the shock to limit travel, but, I think of Colin Chapman's famous saying "Any suspension will work, if you don't let it".

Thanks!

[Santiago]

John, what size offset are you running? The 225/40-17 tire is only 24.1" in diameter and very close to the 210 slicks the FFR blue mule runs up front. They're making it work without flaring the fenders, so we know it works. After overall diameter, the next culprit is offset. I think +35 is the max you can go down under the existing body work.

Best,
-j

[Stickshift84]

I am not as most others are not having trouble fitting the tire under the fender. The problem has been rubbing at full lock into the rear splash guards. Problem is easily resolved with steering limiters on the rack.

Where are your tires contacting the fenders. Pictures help too.

[nuisance]

Thanks guys. The wheels are +40 offset. The tires are hitting the top of the fender cutout, on the outside edge, when they are turned left or right. It will take a 1.5 inch spacer in the shock to stop it, which is about half the total travel.

[Santiago]

Well that is weird... You're offset is fine and overall dia. fine (btw, 15" wheels won't help except insofar as they might help you use a very small tire, since the outside tire dia. is the outside dia regardless of what wheel you run). We're going to need more info - and pics may help supply that. Maybe we can generate a check list:

1. Fender mounting/body panel alignment proceedure: perhaps you figured out a non-standard way to mount them lower than typical?
2. Alignment setting (incl. control arms used): maybe you're at some whack positive camber or your caster is jacked up?
3. Mods: anything you did to the front that hasn't been done/documented yet?

Others might be able to add to the checklist. Seems like a "from-the-beginning" account is in order. FWIW, my current suspect is #2.

Best,
-j

[nuisance]

Well that is weird... You're offset is fine and overall dia. fine (btw, 15" wheels won't help except insofar as they might help you use a very small tire, since the outside tire dia. is the outside dia regardless of what wheel you run). We're going to need more info - and pics may help supply that. Maybe we can generate a check list:

1. Fender mounting/body panel alignment proceedure: perhaps you figured out a non-standard way to mount them lower than typical?
2. Alignment setting (incl. control arms used): maybe you're at some whack positive camber or your caster is jacked up?
3. Mods: anything you did to the front that hasn't been done/documented yet?

Others might be able to add to the checklist. Seems like a "from-the-beginning" account is in order. FWIW, my current suspect is #2.

Best,
-j

Thanks Santiago

First, the questions. I mounted the front bumper with the bottom 1/2" above the extension of the bottom of the frame per the manual. When you factor in making the hood fit, everything else follows along. The fender mounts on an obvious mounting tap on top, and to the front bumper as shown in the manual. And to the door sill (part of the big rear fender piece) where there is a boss to line up with. This picture shows this, taken at full droop - i.e. the shock is fully extended.

full droop.jpg

Alignment is 3.6 degrees castor, and -2.9 camber. I am using 3.5" as ride height because that is what Jim S. told us was used in the race prototypes. Here is a side pic at ride height (and then one turning).

ride height straight.jpgride height turn.jpg

Here is a picture of the tire hitting the fender in a turn. This happens at a one inch bump. There is still 1 3/8" of travel left on the shock, and with the 1:1.4 motion ratio, means almost 2" of tire travel left.

fender vs tire.jpg

Here is a picture of the front suspension. I have not made any changes to the suspension. Everything is attached to the upper (R) holes of course.

susp pieces.jpg

The tire is a Hoosier 225-40/17, and according to TireRack, is 23.8" in diameter. It may be a bit more square shouldered than some street tires.

By the way, I have measured that if you use a tire 22.5" in diameter, the frame will hit the ground when the shock body hits the bump rubber.

Any insights would be greatly appreciated!

John

[Santiago]

Grrrr...damn reality. Everything on paper looks great.

Ok, is this happening on both sides? I'm wondering if it's possible that the entire front end bodywork is aligned piece-to-piece but offset overall. A long shot, but worth checking the other side if you haven't already.

Might want to check with Jim. I know he mentioned the first blue R had a bit of tire rubbing, but I thought it was (a) in the rear and (b) resolved. At the very least, you might want to ask him how much bump travel they're getting when fully sprung. What the springs can do and what the coil-over assy. as a whole will do are 2 different matters. 1" of bump isn't a lot so I can see the concern, but I don't recall what he said they had on the mules.

Best,
-j

[nuisance]

It is the same for both sides. I'm afraid it is real. 13/16" makes sense, since the body and frame are lower relative to the wheels and tires. I suspect that even the S model can have this problem. I think the only savior is fairly high spring rates for the weight.

I will see if I can call Jim and talk to him.

Thanks for writing!

[C.Plavan]

I had to raise my front up because it was hitting also on the fenders. I also have 235 tires though.

I cant go full lock, but I cant on my other race car either, so it has never been a issue.

[Scargo]

Chad, how are you feeling about the tires/wheels at this point? You said you raised the front to accommodate the wheels. You said 235's but whose tires and what size specifically on what wheels? Do you wish for more front tire?

[C.Plavan]

Chad, how are you feeling about the tires/wheels at this point? You said you raised the front to accommodate the wheels. You said 235's but whose tires and what size specifically on what wheels? Do you wish for more front tire?

They are ok and work with my front offset (I think ET38 off the top of my head). I got a tiny bit of rub on the outside lip going through high speed corners, but nothing to worry about since the tire fixed itself. I think if had a et40 it would of rubbed too much. With the 235 I could only get a little over one full wheel turn before it would rub and stop from hitting the inside frame. The only time that is a problem is in the paddock- just make 3 point turns if you need to make sharp turns. On the track, it was no issue at all.
I think on my spare set I'm going with 225/40's Hoosier's up front. Rear 245 or 255.