16" Wheels all round - Offset question
16" Wheels all round - Offset question
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Discussion

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
Right ok.... I know I've posted loads of subjects about wheels and tyres but I have (what I hope to be) the last question.....

Is the offset for the 16" wheels for the later cars that came with 16's all round the same front and rear?

And on the car I own is the offset the same front and back so if I bought 2 rear 16" wheels could I put them straight onto the front of my car? (obviously with the corretly calcultaed tyre size which I think would be 205/50/16 which would give a speedo error of -0.8%)

What I would like to do is replace my front 15" wheels for 16's as this expands the options when it comes to new tyres. I want to get GSD3's for the front to match my rears but they don't come in 15".

else

795 posts

267 months

Tuesday 5th April 2005
quotequote all
I'm in the process of doing exactly the same to mine.

I bought another pair of rear wheels and fitted the wider 245/45 16 SO3s. These went on the rear and then I fitted the original rears to the front. Unfortunately they are too big and rub when manoeuvring over uneven surfaces.

I was thinking of fitting 205/45 16s but haven't got round to it yet. I just put the old 15s back on for now.

Anybody tried either of these sizes?

Podie

46,649 posts

304 months

Tuesday 5th April 2005
quotequote all
Not tried yet, but currently looking for a set of 16s for the front...

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
else said:
I was thinking of fitting 205/45 16s but haven't got round to it yet.


From the website that I used to calculate tyre sizes the closest would be a 205/50/16 as the difference is --0.8%. So I think it said that when I was doin 60 the true speed would be 60.5. With such a minimal diameter difference and the same width tyre there should be no rubbing of body work.

I stand to be corrected on any of this, hence the post.

Ribol

11,993 posts

287 months

Tuesday 5th April 2005
quotequote all
The offset is the same so yes you can fit rear rims on to the front. Tyre size for the front is 225/45ZR16. You will also need rack stops which will increase the turning circle to Boeing 747 proportions.

Not too sure where you are coming from with the speedo theory, you lost me on that one.

M@H

11,298 posts

301 months

Tuesday 5th April 2005
quotequote all
Ribol said:
Not too sure where you are coming from with the speedo theory, you lost me on that one.


Me too

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
Ribol said:
The offset is the same so yes you can fit rear rims on to the front. Tyre size for the front is 225/45ZR16. You will also need rack stops which will increase the turning circle to Boeing 747 proportions.

Not too sure where you are coming from with the speedo theory, you lost me on that one.


There's a website that calculates tyre sizes based on adjusting the tyre width or the wheel diameter.

If you go from a 205/55/15 tyre/wheel combo to a 205/55/16 the overall rolling circumference of the wheel will be incresed as you are putting the same aspect ratio-tyre width on a wheel 1" bigger.

Does that make sense? I think it's 55% of the tyre width on a 15" wheel so you have to adjust down to a 50% aspect ratio to maintain the same circumference.... sounds confusing but probably the way I explain it.

If you don't do this adjustment you will affect the distance travelled for each rotation of the wheel which I believe affects the acuracy of the speedo.

I was going to fit 205/50/16 tyres as from the said calculator the accuracy is only a little bit affected and there should be no body contact as the width of the tyre is exactly the same.

M@H

11,298 posts

301 months

Tuesday 5th April 2005
quotequote all
Err.. Speed calculation is related to the Rear wheel diameter, not the front


>> Edited by M@H on Tuesday 5th April 16:06

mick_coupe

332 posts

275 months

Tuesday 5th April 2005
quotequote all
A good site for tyre size calculations

www.tyresave.co.uk/tyresize.html

Mick

HarryW

16,028 posts

298 months

Tuesday 5th April 2005
quotequote all
No wonder the chim 16" wheels are getting difficult to get hold of .

Harry

else

795 posts

267 months

Tuesday 5th April 2005
quotequote all
Unfortunately SO3s aren't available in 205/50ZR16 but 205/45ZR16 are so that's what i think I will go for. A bit narrow for a 7.5" rim though.

>> Edited by else on Tuesday 5th April 16:43

Ribol

11,993 posts

287 months

Tuesday 5th April 2005
quotequote all
M@H said:
Err.. Speed calculation is related to the Rear wheel diameter, not the front


In his defense some cars(very few) work off the front wheels, not the back.
Sadly a TVR ain't one of them

the dodger

2,376 posts

292 months

Tuesday 5th April 2005
quotequote all
Ribol said:

M@H said:
Err.. Speed calculation is related to the Rear wheel diameter, not the front



In his defense some cars(very few) work off the front wheels, not the back.
Sadly a TVR ain't one of them

er actually speedo sensed at the prop (early cars) or drive shaft (later). I accept this is connected to the rear wheel so M@H is factually correct.

Pies

13,116 posts

285 months

Tuesday 5th April 2005
quotequote all
I cant understand why you lot cant find 16" wheels,I've found plenty

petros

2,441 posts

258 months

Tuesday 5th April 2005
quotequote all
Running 245 45 16s on the Rear and 225 45 16s on the Front of my Chim with no problems. peter

Ribol

11,993 posts

287 months

Tuesday 5th April 2005
quotequote all
the dodger said:

Ribol said:


M@H said:
Err.. Speed calculation is related to the Rear wheel diameter, not the front




In his defense some cars(very few) work off the front wheels, not the back.
Sadly a TVR ain't one of them


er actually speedo sensed at the prop (early cars) or drive shaft (later). I accept this is connected to the rear wheel so M@H is factually correct.


Really, you learn something new every day

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
M@H said:
Err.. Speed calculation is related to the Rear wheel diameter, not the front


>> Edited by M@H on Tuesday 5th April 16:06


Said I stood to be corrected

Anywho...... I want to stay as near to standard as I can...

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
Pies said:
I cant understand why you lot cant find 16" wheels,I've found plenty


Really... Share the source

shortlad

Original Poster:

529 posts

281 months

Tuesday 5th April 2005
quotequote all
else said:
Unfortunately SO3s aren't available in 205/50ZR16 but 205/45ZR16 are so that's what i think I will go for. A bit narrow for a 7.5" rim though.

>> Edited by else on Tuesday 5th April 16:43


The original fronts are 7.5x15.... According to an artical I read that Jools helped on.

GSD3's (the prefered choice of the factory these day ) are available in 205/50/16.... checked today. They will match my new rear tyres.

spend

12,581 posts

280 months

Tuesday 5th April 2005
quotequote all
Mine are ET42(F) & ET33(R) IIRC. Only Cerbs have same front & rear as standard I think (ET35 on my set of 16"). I believe my 18" spiders are same offset as the 16".

Cerb ET35 has hardly any clearance on my rears - I wouldnt risk using them, just got a good set of tyres spare.

I think the original offsets should be ET25 (F) & ET 42 (R), peugot & ford or something.


Dave