clubstylus

I was looking at one of phil's posts on Locost about scrub. My car is very twitchy on bumpy roads, especially under breaking. Someone said that could be the scrub/offset issue. My cousin reckons the same but is unable to explain to me how. Someone on Locost gave a basic description. I just wondered what the correct off set should be for a 15 x 7 wheel.

Also how do i check it?

My Phoenix runs 7x15, soon to change to 8x18, my choice of wheels was very limited as I live in Asiaa and 108 PCD is not common, so I was forced to buy what I could get and then use spaceyrs to set themmup to give the right offset, At the back I aimed to keep about 12 mm between the tyre wall and the lower link, this gave enough clearence for the bit of movment in the back axil. At the front I had to look at clearing the outside edge of the front wing, so I used that as a reference, I didn't find the wider wheels/change in offset made any diffrence to te cars stability and my car will do 170MPH, I'd suggest your on the wrong track(no pun) worrying about offset. My wets are 6x14 and are set up the same way (from the lower link) I change the spacers and no instability

You'd be amazed at the differing off-sets many ' SYLVA ' owners run without any ill effect -- however , with our Escort M2 set-up and 15x7 wheels , I run ET15 and Matt runs ET12 so Matt's wheels project 3mm's each side wider than mine . (ie. ET zero would make my wheels project 15mm's wider each side of the car )The rule is ---- bolting face dead centre of wheel = no off-set . Bolting face towards the outside of the car = narrower track Bolting face towards the inside of the car = wider track
If you run an off-set where the bolting face is well towards the centre of the car = wide track , on the front end , then you'll get instability.

I would guess that with the symtoms you describe that too little castor is the culprit
The only other culprit may be too low a tyre profile perhaps 40 profile 45 has been used without drama

To measure off-set , put a steel rule across the inside of the wheel rim (missing the tyre ) then measure from that to the bolting face . If it's more than half the rim width by , say , 5 mm's then your off-set is ET5 --- got it

Thanks Rob, i ordered all of my wheels with an ET45, the reason being i am using a wider rear atlas axle and needed the wheels to stick in under the arch as much as possible so the rear wheels didnt rub on the arch. I didnt want to order different wheels for the front and rear so run spacers on the front. But only about 20mm of spacing so i still have an ET of about 25.

My tyres are the same as yours, 205/50/15

I have wondered if its my roll bar being too stiff so i will try disconnecting it and see if it makes any difference.