Is it possable to change a wheel\'s offset?

[Wombat-007]

Hi guy\'s, does anyone know if a wheel\'s offset can be changed by machining from a wheel specialist?
I currently have a set of Prodrive alloys (17 in with recomended tyre width and height front and rear), the rears are spot on, but the fronts rub the arches on the outer part of the tyre.
I was wondering if it\'s possable to have the wheel centres machined as I believe to offset at the front is too great and I don\'t really want to change the wheels.
What is the best way to measure a wheels offset to, so I can double check.
Any advice is much appreciated

[Jit]

hey phil,
dont think youre gonna be able to remove the amount you need by machining and i wouldnt really recommend doing it either! You thought about rolling the arches?

[SiH]

You can have them machined, but it totally depens on whether or not the wheel will support it - i.e. how thinck the face is.
There is also the issue of the centre bore, and if there will be sufficient \'meat\' to locate the wheel (although this isn\'t vital)


How wide are the wheels, and how wide are the tyres? Depending on how much clearance is needed, i personally would look at possibly running a narrower tyre, with a stretch on the front, and/or rolling the lip, as suggested above,
If this still doesn\'t work, then the next solution would be some wider wings.

Got any piccies of the \'issue\'?

[Wombat-007]

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Thanks for your replys, the wheels are
front 17x8.5 with 235x45 tyres
rears 17x9.5 with 255x40 tyres.
These seem to be the recomended wheel tyre combination.
 
I believe these wheels were originally for a Suburu as they are Prodrive and as such beleive it to be the offset to be the problem.
There seems to be no issue with the wheel arches, just the front inner wing cover.
 
Please see photo\'s attached, there appears to be more than enough metal to allow some trimming, any thoughts?
 
Would any of you know anywere south London area I could get the wheel offset measured and machined if needed.
 
Thanks for you help as always

[Martiny]

Is there a way to modify the arch lining rather? I would never skim a wheel like that,(or use spacers) - it\'s compromising safety.

[antnicuk]

i would look at the modding the arch/liner before i touched the wheel.  A 235/40 tyre would help a lot,  where is it touching,?

[SiH]

Indeed - sorry - i wouldn\'t rea;;y advocate machining, but it is possible.
However, i have no problem with using spacers at all, but only good quality ones - I rand a set for nearly 2 years n my previous car, and I know a LOT of people that run them with no issues whatsoever.

Where is it rubbing the liner - inboad or outboard? and is it only on lock?
If it\'s rubbing the arch liner on the inboard side then spacers may solve your problem, rather than machining - if it\'s inboard the last thing you want to do is increase the offset - you need a lower offset - so spacers.

What is the original tyre size on FD\'s? Not sure - but if you want to keep the correct rolling radius then running a lower profile isn\'t the right way to go about things.
If youa re experiencing scuffing of the liner you could stretch a 215 onto an 8.5 with no issues

[RemarkLima]

They\'re the right sized tyres so it should be all OK, do you know the offset of the wheels as AFAIK the offset for 17\'s should be 45.

Is the car on aftermarket suspension? Is it too low for the springs hence the wheel touching the liner? Or is it when you turn corners?

Also, agree spacers are fine, as long as they\'re decent ones and if there\'s a large space involved they have another hub ring and come with longer studs so the nuts have enough thread to hold onto.

[SiH]

They\'re the right sized tyres so it should be all OK, do you know the offset of the wheels as AFAIK the offset for 17\'s should be 45.

Offset is dependant on wheel width, rather than diameter It\'s effectively the distance from the wheel centreline to the hub face.
You can sometimes get round rubbing issues by running a narrower tyre for that extra bit of clearance

EDIT: Ok, according to this post:
http://www.mazdarotaryclub.com/forums/showpost.php?p=27097&postcount=7
The standard diameter for the front wheels is 650mm.
Your 235/45/17 gives you a tyre diameter of 643mm (~1%), which is close enough
I wouldn\'t go for a 40 profile, as this will give you a diameter of 619mm - that\'s 5% out, which is, imho too much. So i wouldn\'t look at changing the profile - you\'d be surprised at the effect even a change like that can have on the handling.

[RemarkLima]

Exactly! The sizes he has are the Mazda sizes for the 17" rims, which would affect handling tons and so I\'d not change it TBH.

So I\'d look at keeping the tyre sizes and altering the wheels, ride hight, suspension stiffness etc...

[SiH]

Yup, but he could run a narrower tyre on those rims with a higher aspect ratio and keep the same rolling radius

[shaunwil]

Just out of interest, have you had the car wheels aligned ? Tyre looks very square to the body. What should the camber be set to ?

I would agree that you need to roll the arches because it can\'t be touching too hard.

Im running 225x45x17 up front and haven\'t got any issues with kuhmo ku15\'s

Shaun

[antnicuk]

why would changing the rolling radius of the front (non driven wheels) effect handling?

it wont effect the speedo reeding,  i thought rolling radius issues were important for accurate speedo reading and diff issues on the same axle or 4*4 cars.  

Can anyone explain please

[shaunwil]

There is less resistance to change in direction, less friction stopping the tyre from changing direction.

As long as the rears match the original rolling radius then the speedo will be ok.

Although alot of people say that you should keep the rolling radius as close as possible between rears and fronts to keep the car stable.

Shaun

[Wombat-007]

Phew! Decisions Decisions.
Thanks for all the input guys, think I may try 40 profile on the front as  this seems to be the easiest fix.
The tyres are only rubbing the front on the arch liners on full lock (both directions) on the outside of the tyre only.
From that I presumed the offset to be too great. Other RX\'s I\'ve seen appear to have the front wheels slightly further in the arches.
Not too keep on modifying the liners as I believe the wiring loom runs under the nearside wing.
 
Think I need to get the whole car set up with a 4 wheel alignment, but hope to replace some of the dreaded pillowballs first and might as well go whole hog and poly bush front and rear too. I gather this isn\'t the most fun job in the world, but hey, it\'s going to be worth it in the long run.

Thanks again everyone, will let you know how I get on