Wheel fitments? Hmm..

[cj2013]

Just thinking...

I know that the 'ideal' offset for a puma is E35 (or ET35 if you will), and E40/ET40 is often known to just not fit right at all...


But ford offered ET40 fitment as an option??

 

[Ian G]

On wider wheels.

If my recollection of suspension geometry serves me correctly, its do to with the scrub radius which in turn affects steering feel and stability, the additional 5mm will bring the wheel further in the arch and maintain a negative scrub which is for a number of reasons good in a FWD car.

Note also on the 7" width they are back to ET35, presumably because there is insufficient clearance on the suspension components, may be aesthetic reasons or may be that they figured people who were going for 215s on a 7" rim were already less interested in feel and more interested in outright grip.

 

[cj2013]

Perhaps.

As I've told you already, I fancy some of the Cosworth alloys.. found quite a few of the 16's, less of the 15's, all obviously in the common ET40 x 6.5J...

From a number of threads people talk about 40's being a bit of a bodge that cocks the handling stance up, but seeing the catalogue has me confused now :/

I did wonder why they 35'd the 7J, but guess that's the clearance as you mentioned.

I know that the offset difference will slightly affect the Ackerman angles a little though. Worrying how much of my degree I can only vaguely remember

 

[Wild E. Coyote]

You are forgetting that we are talking 6,5" wheels here. ET (EinpressTiefe, press-in value would be a rough translation from german) or offset of 34 mm means that your pickup point if the wheel in question is translated by 34 mm to the outside leaving you with 42,2 mm of wheel on the outside. As the width of your wheel is 6" (152,4 mm) inside you have 110,2 mm.
Now, if you use 6,5" wheel (165,1 mm) with ET40, you would get almost identical 42,55 mm on outside and 122,55 mm on inside.
To sum it up: it would look almost identical and shouldn't affect driving quality at all. As Ian G pointed out, you want to maintain the same scrub radius, and as the outside width value of your wheel is different for 0,35 mm it is practically the same.

If this is confusing, I can add some drawing to clarify it

 

[RICHARD MANSFIELD2]

Hi,
I have run 17"x7" wide rims with ET40 with 30mm lowered springs with no problems what so ever. This info may be of help.
Regards
Richard Mansfield

 

[cj2013]

You are forgetting that we are talking 6,5" wheels here. ET (EinpressTiefe, press-in value would be a rough translation from german) or offset of 34 mm means that your pickup point if the wheel in question is translated by 34 mm to the outside leaving you with 42,2 mm of wheel on the outside. As the width of your wheel is 6" (152,4 mm) inside you have 110,2 mm.
Now, if you use 6,5" wheel (165,1 mm) with ET40, you would get almost identical 42,55 mm on outside and 122,55 mm on inside.
To sum it up: it would look almost identical and shouldn't affect driving quality at all. As Ian G pointed out, you want to maintain the same scrub radius, and as the outside width value of your wheel is different for 0,35 mm it is practically the same.

If this is confusing, I can add some drawing to clarify it

It isn't confusing at all, as I am degree qualified in an area which includes this subject - I haven't used the vehicle dynamics (suspension & steering geometry) side for a couple of years so I double guess myself.

My confusing is that the mathematics of it makes sense, but there are conflicting posts.

To an extent, you have contradicted yourself here with what is posted in http://www.projectpuma.com/viewtopic.php?f=20&t=20988&hilit=et40, saying that you should stick to the same offset?

Also Dal here:

http://www.projectpuma.com/viewtopic.php?f=20&t=18055&hilit=et40

a topic here:

http://www.projectpuma.com/viewtopic.php?f=20&t=17312&p=219461&hilit=et40#p219461

I know that it shouldn't make much difference on paper, but people are saying that it ruins the car's handing. I'm just wondering why, if that's true, Ford offered the option?

 

[Wild E. Coyote]

It isn't confusing at all, as I am degree qualified in an area which includes this subject - I haven't used the vehicle dynamics (suspension & steering geometry) side for a couple of years so I double guess myself.

My confusing is that the mathematics of it makes sense, but there are conflicting posts.

To an extent, you have contradicted yourself here with what is posted in http://www.projectpuma.com/viewtopic.php?f=20&t=20988&hilit=et40, saying that you should stick to the same offset?

Also Dal here:

http://www.projectpuma.com/viewtopic.php?f=20&t=18055&hilit=et40

a topic here:

http://www.projectpuma.com/viewtopic.php?f=20&t=17312&p=219461&hilit=et40#p219461

I know that it shouldn't make much difference on paper, but people are saying that it ruins the car's handing. I'm just wondering why, if that's true, Ford offered the option?

If you read that carefully, it says you should aim for the sam radius of rotation for a steering wheel. And that is exactly I was calculating in this thread showing it is virtually the same. OK, fair enough, I wasn't clear enough about it in the prevoius thread stating you should aim for the same ET

My point: 6,5J wheels with ET40 are viable replacement for a 6J ET34 wheels. Having said that, other then cosmetic purposes I don't see a point in going from 6 to 6,5 inch widht wheels and keeping at the same time 195 mm tyres…

Only my two cents, as always

 

[Wild E. Coyote]

I know that it shouldn't make much difference on paper, but people are saying that it ruins the car's handing. I'm just wondering why, if that's true, Ford offered the option?

I don't have any experiences myself, but would think that that would go for a later style fiesta wheels that are 6Jx15 but have ET of 45 mm. In that case you are translating your tyres towards centre of a car and reducing track and messing with your suspension geometry...

 

[Snowcol]

Wow - Interesting but way over my head! I have recently bought a set of TSW wheels which are 15" x 6.5J and while I don't know precisely the ET measuring the wheel and comparing with the standard it appears these are approx ET 20. When I fit them on the car they seem fine with the outer face of the tyre either in line or marginally inside the line of the wheel arch. Using standard 195 x 50 x15 tyres

I reckon this set up should widen the footprint of the car and improve handling.

Question for those with greater knowledge than me however is - do you forsee any issues with this set up?

I intend putting coilovers on to lower/stiffen the car and am consious that I will need to watch I dont take the front down to a point where the tyres catch on the outer edge of the wing. I won't know till I try it how far I can go before that becomes a problem - if it does become a problem.

Your thoughts would be appreciated.

 

[Sweep]

Perhaps.

As I've told you already, I fancy some of the Cosworth alloys.. found quite a few of the 16's, less of the 15's, all obviously in the common ET40 x 6.5J...

Assuming you're referring to Escort, they only came in 16".