Front Tire Vs. Rear Tire Wear

[palomar]

Issue: Front tire appears more "shagged" than rear after canyon or track riding.

Bike: 2003 R1

Tire: Metzeler M1

Setup: 35 mm front, 25 mm rear sag

Springs / valving: Circuit 1 front, Penske rear (front sag was 43 mm with preload adjuster maxed out with my 210 lb. weight)

 

Whe I was running the bike on the stock 208 ZRs and stock suspension, the rear tire would always look more abused after a quick run through the canyons or a track day. After the suspension and tire change, the front tire has consitently looked more shagged after spirited riding.

 

The bike feels good but I can't help but wonder if I have something out of balance. Perhaps tire pressure or ride height. I did raise the rear ride height about 8mm after the suspension change because the front felt slower after reducing the sag in the front from 43 mm to 35 mm.

 

Any comments based on experience, etc. would be appreciated.

 

WHC

[Balistic]

Tire wear front to rear can be an indicator for weight bias. As a norm I am twice as hard on the rear in racing conditions. At the school when we run them bald the ratio is about the same.

If you are tearing up the front and the suspension is properly set-up (BIG IF) then the wear in your front could be telling you that the front has too much weight on it. There are other indicators like a tendency to push the front off the gas or being twitchy down the straights (not enough trail) but sever front tire wear is either bad damping set-up or weight bias.

Will

[palomar]

Will,

 

Thanks for the input. It is greatly appreciated.

 

Front weight bias makes sense. The ride height increase I made in the back may have contributed to this.

 

I put a fresh front on last night. I'll take it up to the mountain this weekend, ride it Saturday and photograph it. Sunday I'll clean off the hanging bits, drop the rear two mm, ride again, photograph and compare. Maybe I'll see something from this.

 

Would it be worth my time to make a static front / rear weight bias measurement? My employer has a set of scales designed for setting up race cars that will allow me to put a separate scale under each wheel and get individual weight readouts while I sit on the bike.

 

WHC

[Balistic]

The only bike I ever weighed was at 51 front 49 rear, but I have no frame of reference for such a measurement on a newer bike. I do it by feel and tire wear.

I thought you dropped the front, if so that is the first adjustment to do. Start picking the front up, with what you have said here I would start back at the stock ride height and go from there.

Will

[palomar]

Will,

 

I ran the new front last weekend on mt. palomar with 2 psi higher pressure than I was using before. I decided to put off messing around with the ride height. My cold pressure for the rides were: 31 psi rear, 33 psi front. I had been running 31/31.

 

I rode both saturday and sunday with this setup and the front tire looks much more like the rear without the extra strands of rubber hanging off.

 

Thanks again.

 

Bill

[Balistic]

Will,

 

I ran the new front last weekend on mt. palomar with 2 psi higher pressure than I was using before. I decided to put off messing around with the ride height. My cold pressure for the rides were: 31 psi rear, 33 psi front. I had been running 31/31.

 

I rode both saturday and sunday with this setup and the front tire looks much more like the rear without the extra strands of rubber hanging off.

 

Thanks again.

 

Bill

I think I see another problem. Your rear pressure is a bit high. I run 28 or 29 rear on the track without overheating the tire. At 31 the tire isn't contorting as much as it should which could keep the rear up and put too much weight on the front too.

Do you ever do cold to hot pressure differential? This would give you an idea of weather the tire was getting up to temp. You should get 6 to 8 psi rise at best. if it's more than eight you need to bump the pressure up and less than 6 lower it, with 28 being the least to use (rear) and 30 ( front).

Will

[palomar]

Will,

 

I haven't been checking my differential pressures. I'll look at that and see how I go.

 

Thanks for the input. I knew there should be an ideal pressure differential, but I didn't know what it should be.

 

Does this value vary much from tire to tire? I put a set of Rennsports (RS2 front RS3 rear) on last Sunday with the same pressure (31 rear / 33 front). Next week I'll measure these cold and then heat them up in the corners and see what I get. I'll be at big willow on Monday the 24th and I'll check the differential again there as well.

 

Thanks again,

 

Bill