Negative Offset Wheels

[Glade]

My Westfield has 7" wide wheels. The details I have from when they were made is that the hub plane is 4" from the front of the wheel. Arches, cycle wings etc are set for these wheels so different ones may rub or not fill the arches.

So I take this to mean...

7" wide / 2 = 3.5" to centre line (zero offset)

3.5" - 4" from front = -0.5" = -12.7mm....

so -13mm offset?

If I want to get spare wheels I think I'm going to have to buy ET15 wheels and use 25mm spacers and they'll be about right?

Am I right???

[gtmdriver]

Your working out is fine.

Did you actually measure the overall rim width or are you using the quoted dimension because rim width can often be measured from the inner rim faces where the tyre fits rather than the outside face.

This could affect your measurement slightly.

[JontyR]

Don't run spacers. If you are getting a wheel then get the correct offset from the outset.

You need to run measure correctly though. Your workings are correct, but you need to put a flat bar across both sides of the wheel, making sure it isn't disturbed by the tyre. Then measure the true width and not the inner edge that is used by the wheel manufactures. Plus you need to measure in mm so you don't lose accuracy with the conversion.

[Glade]

What's the reason for not running spacers.

I can't see anywhere online that sells negative offset wheels. Any ideas?

I understand about measuring the outer edges of the wheels.

Thanks!

[JontyR]

99% of wheels are running a negative offset.

I dont like spacers as I think it puts too much strain on the studs. Just get the right offsets in the first place, and then it will work out of the box

[andygtt]

many spacers run a 2nd set of studs which is perfectly ok... just adds weight

[JontyR]

Do they not put additional forces onto the bearings causing them to fail earlier? Also moving the wheels out isnt necessarily going to improve the handling, the geometry is going to stay in the same place...so you wont be effectively using the tyre patch. I could be wrong?

I just think that if you are going to go to the expense of fitting new wheels...then rather than fit spacers why not get the offsets right in the first place.

[Mr2Mike]

JontyR said:

99% of wheels are running a negative offset.

I really don't think they are! Almost all FWD cars (which is the majority of cars) will have wheels with a positive offset.

[JontyR]

Mr2Mike said:

JontyR said:

99% of wheels are running a negative offset.

I really don't think they are! Almost all FWD cars (which is the majority of cars) will have wheels with a positive offset.

I stand corrected....the majority of cars I have worked on have all been negative offset....most of which have been rwd...so sorry

[Rothgo Wooft]

Mr2Mike said:

JontyR said:

99% of wheels are running a negative offset.

I really don't think they are! Almost all FWD cars (which is the majority of cars) will have wheels with a positive offset.

I just had a look at my handily placed Rush wheel specification, and its talking about 'inset' and 'outset', rather than offset. Most cars have the hub contact surface nearer the outside (like my front wheels in my manual), which is 'inset', apparently. The rears are a little outset with the wide arches. Ooh! A bit like these http://pistonheads.com/sales/1732242.htm <ahem>

In terms of offset, I guess it all depends on what is positive... So which way is it?

[Glade]

JontyR said:

Do they not put additional forces onto the bearings causing them to fail earlier? Also moving the wheels out isnt necessarily going to improve the handling, the geometry is going to stay in the same place...so you wont be effectively using the tyre patch. I could be wrong?

I just think that if you are going to go to the expense of fitting new wheels...then rather than fit spacers why not get the offsets right in the first place.

hmm not sure about aditional stress. The plane of the hub face will be in the same position relative to the rim/tyre...

This isn't to increase track, but keep it the same with more easily sourced wheels.

[JontyR]

Rothgo Wooft said:

Mr2Mike said:

JontyR said:

99% of wheels are running a negative offset.

I really don't think they are! Almost all FWD cars (which is the majority of cars) will have wheels with a positive offset.

I just had a look at my handily placed Rush wheel specification, and its talking about 'inset' and 'outset', rather than offset. Most cars have the hub contact surface nearer the outside (like my front wheels in my manual), which is 'inset', apparently. The rears are a little outset with the wide arches. Ooh! A bit like these http://pistonheads.com/sales/1732242.htm <ahem>

In terms of offset, I guess it all depends on what is positive... So which way is it?

Negative Offset



Positive Offset



Hope that helps

Edited by JontyR on Friday 18th June 20:41

Edited by JontyR on Friday 18th June 20:42

[JontyR]

Ive just contradicted my own thoughts on what is what!

So with the above picture in mind....I guess what I have been referring to as negative is actually positive! Is there an econ for something more than getting your coat? Thankfully all of the wheels I have ordered have turned up correct

[andygtt]

JontyR said:

Do they not put additional forces onto the bearings causing them to fail earlier? Also moving the wheels out isnt necessarily going to improve the handling, the geometry is going to stay in the same place...so you wont be effectively using the tyre patch. I could be wrong?

you are correct if you are changing the possition of the wheel by fitting spacers... but in this case the car is designed for the offset so having a spacer to get the same wheel possition will have no effect on geo or bearing life as the wheel will be in the same possition.

The only difference will be the extra unsprung weight, which will react same as fitting heavier wheels.

JontyR said:

I just think that if you are going to go to the expense of fitting new wheels...then rather than fit spacers why not get the offsets right in the first place.

I agree totally... the spacer will add weight which isn't great
But may be significantly cheaper to fit spacers and you might have a greater range that allows a lighter wheel offseting the extra weight.

[Rothgo Wooft]

JontyR said:

Hope that helps

But which one is negative and which is positive?

[JontyR]

Rothgo Wooft said:

JontyR said:

Hope that helps

But which one is negative and which is positive?

I could swear it had a label on there earlier!

I think this thread has proved that senility has set in!!