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Rear tyre hitting arch

woodsy - 19/10/21 at 07:01 AM

I seem to remember my last MK Indy suffered with the rear drivers side tyre hitting the arch but that was a few years ago. I've seen a really nice example for sale but this seems to have the same problem.
What is the remedy ? Run wider arches , suspension check , slightly narrower tyres ?
I'm a bit clueless when it comes to things like this so please be gentle
[img]free screen capture software[/img]

Slater - 19/10/21 at 07:12 AM

Might be easier to remount the arch and move it upwards slightly and maybe rotate it anti-clockwise. Sometimes the arches get mounted the wrong way round too, they are handed, maybe that is the issue. But we'd need to see more pics taken from further away to check.

40inches - 19/10/21 at 08:11 AM

Check that the arches are the correct way round, the sloping part should be at the front.

Description

woodsy - 19/10/21 at 08:18 AM

The only other pic that i've been sent is this one, the bottom looks lined up fine

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roadrunner - 19/10/21 at 09:20 AM

Either the arches are mounted to far forward, the wheels and tyres are too big or the suspension is out.
I had 17" wheels on my Indy but with low profile tryes and they fitted, just.

myke pocock - 19/10/21 at 09:53 AM

Looks like you have plenty of room to lift the arches up. I recon they have been fitted too low.

Slater - 19/10/21 at 11:53 AM

quote:
Originally posted by myke pocock
Looks like you have plenty of room to lift the arches up. I recon they have been fitted too low.

I agree, looks like the leading edge is in the right place, i.e. level with the bottom of the car, but the trailing lower edge might be set too low, see my pic, the rear of the arch should be mounted about 30mm above the bottom of the rear tub.

[img]

diffuser 64 17may20 [/img]

Also the very top of my arch is 30mm below the top of the rear tub.

Either that or the tire is too big.....

woodsy - 19/10/21 at 12:12 PM

quote:
Originally posted by Slater

quote:
Originally posted by myke pocock
Looks like you have plenty of room to lift the arches up. I recon they have been fitted too low.

I agree, looks like the leading edge is in the right place, i.e. level with the bottom of the car, but the trailing lower edge might be set too low, see my pic, the rear of the arch should be mounted about 30mm above the bottom of the rear tub.

[img]
diffuser 64 17may20 [/img]

Also the very top of my arch is 30mm below the top of the rear tub.

Either that or the tire is too big.....

It looks like you are right, they sit flush with the rear tub. Lifting it 30 mm should help
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woodsy - 19/10/21 at 12:18 PM

Also it's running 225/50 x 15 on the rears ,from what i have read most are running 205 width tyres.

nick205 - 19/10/21 at 05:56 PM

Having built an MK Indy myself and looking at the photos I'd say:

1. The rear arches need repositioning further back.
2. The tyres are too wide and the wheel offset may be wrong. The tyres appear to be sitting proud of the rear arches.

1 isn't that hard to do.
2 may prove expensive if you have to replace tyres and wheels.

Many people seem to get better handling from their cars with 13 or 14 inch wheels. 13 inch wheels may no clear the brake calipers. I fitted 15 inch wheels on my MK Indy (pics in my archive).

JoelP - 22/10/21 at 08:06 AM

I'd be tempted to just trim the arch. Check clearance to the light wiring.

myke pocock - 24/10/21 at 11:03 AM

I recon trimming the arch sufficiently would weaken them as they most likely have a flange return that would need to be cut away.

indykid - 25/10/21 at 09:11 AM

quote:
Originally posted by myke pocock
I recon trimming the arch sufficiently would weaken them as they most likely have a flange return that would need to be cut away.

I linished the returns off the inside of my rear arches to fit 205 tyres on et38 7" rims and there's no issue with strength. Cutting into the face might look a bit scrappy though as you'd see the cut edge. I expect the return has already been taken out of these arches.

Re Slater's comments about positioning the arches, mine are flush with the bottom of the tub front and back and everything fits.

I agree with Nick on the problem and the solution. Fit narrower tyres or change the offset of the wheels to fix the problem. Move the arches back for aesthetics if nothing else, but I don't think those wheels/tyres will ever work with arches of that width without rubbing.