84 replies to this topic

[Paulus H]

By my calculations. If it is a good idea and I am not endorcing this for a moment... But if it is a good idea to run 195 fronts on std wheels, in other words for every inch of wheel width (5.5 inches) there would be 35 mm of tyre (195 divided by 5.5 = 35). Then 8 inch rear wheels would be able to handle 285 tyres. On the other hand.... A 7 inch front tire fitted with 195 tyres has 28 mm of tire per inch of wheel. A 8 inch rear tyre with 225 tyres also has 28 mm per inch of wheel. Or on other cars... 911 GT3 RS Front 27 mm of tyre per inch of wheel width. Rear 27 mm of tire per inch of wheel width 458 Italia, Front 28 mm of tyre per inch of wheel. Rear 28 mm of tyre per inch of wheel Or is the above for another post altogether..? Best regards, Paul

[siztenboots]

rear et35 almost certain to rub the arch liner and the chassis rail, even on standard suspension. front, again depending on tyre sizes its still quite likely to be very close on full lock.

[JL37]

Although a some of us use a 195 tyre on the front of our standard wheels, i think it's best to look at what Lotus designed into our cars as the best starting point. it's a little misleading to just look at mm of tyre per inch of wheel, because in many cases tyres actually have a different actual width than the size they advertise it as . Also the profile of the tyres will help dictate the contact patch and characteristics of the tyre, as well as how the car is set up and ultmate grip of the tyres. Lotus optimised a 175 for a 5 1/2 inch wheel, and a 225 for the 7.5 inch wheel. Therefore for a 7 and 8 inch wide respectively, it would probably be optimised around a 195/205 for the front, and a 225/235 for an 8 inch rear. Also there is greater tolerance if you really wanted to fit tyres wider or narrower than that, but as you say it's best to try to optimise your tyres for the wheel width as a good starting point.

[iVXT]

rear et35 almost certain to rub the arch liner and the chassis rail, even on standard suspension.

front, again depending on tyre sizes its still quite likely to be very close on full lock.

So standard vxr speedlines et35 rub the inner arches on the rear then, why did they use that offset then?

Did people also have rubbing problems with the comps from last group buy then?

Cheers.

[siztenboots]

i've also seen the wheel rim rub on the adjuster knob on a gaz

vxr with speedlines, R888

[iVXT]

Thanks for posting the pic up. I notice this is on nitrons so take it a bit lower than standard but either way rubbing not good. I always get a bit mixed up with offsets even when think got it clear in my head! So lowering the offset from et35 to et30 would move wheel 5mm further away from inner arch but would this cause any probs with being nearer outer arch then? Nothings ever straightforward is it, I though if we matched vxr sizes & offsets we'd be sorted! Cheers.

[siztenboots]

Thanks for posting the pic up. I notice this is on nitrons so take it a bit lower than standard but either way rubbing not good.

I always get a bit mixed up with offsets even when think got it clear in my head!

So lowering the offset from et35 to et30 would move wheel 5mm further away from inner arch but would this cause any probs with being nearer outer arch then?

Nothings ever straightforward is it, I though if we matched vxr sizes & offsets we'd be sorted!

Cheers.

yes et30 negative from the wheel centre line would move wheel 5mm further from centre compared to et35. you would probably put in a good 2 degrees of negative camber anyway so never been a problem for me , you can always trim back the black plastic "spats" part of the outer arch, I run quite a lot of rear toe-in , so the back of the wheel kicks out a lot more.

Edited by siztenboots, 03 November 2010 - 12:01 PM.

[davemate]

out of interest, what were the old group buy OZ wheels, the same as the thorney TD's i assume? possibly in the market for a new set of wheels at some point...

[Steve B]

Well my rd's are thorney / standard VX spec and I run stock ride height and have been known to bottom the suspension out and I've never had any rubbing.

[Paulus H]

Dito, TD's or Compo's std suspension. No rubbing. Paul

[JL37]

Yes i just want to add

My standard wheels and suspension show rubbing, but this is through bottoming out when pushing the car hard. Couldnt believe how my arches looked after i went to the Nurburgring! I suspect you will get this with any wheel combo if you run the car hard enough. I also spoke with Compomotive on the issue, the answer is below. Personally i am going to stick with ET35. If Lotus/vauxhall chose this and had a 20 mm lower ride height on the VXR, then you can be sure it is the optimum offset, and wheel rub will happen in the wrong circumstances with even standard set up.


HI Jason


Well our previous fitments and the last ‘group buy’ all ran with et35 rear offset, and as far as I'm aware no-one came back to us complaining of any rubbing issues. It would not be a problem to machine the offset to et30 should anyone want the extra 5mm track and it will not affect the appearance of the wheel in any way but we have not supplied this rear offset before so have no frame of reference.



If it’s of any further help , {assuming my information is correct this end} the VX220 came with a 7.5x17 rear wheel at offset et36 as an O/E fitment.

I have worked out the full offset measurements for you below. Using the O/E fitment as a starting guide these measurements will give you the new wheel positions in relation to the O/E wheel position.


O/E wheel 7.5x17 @ offset et36. Wheel backspace 142mm. Wheel outboard 70mm approx.


MO1783 8x17 @ offset et35. Wheel backspace 148mm. Wheel outboard 77mm approx.

Or

MO1783 8x17 @ offset et30. Wheel backspace 143mm. wheel outboard 82mm approx.



*wheel backspace dimension taken from wheel mounting face to outer edge of inner rim.

*wheel outboard dimension taken from wheel mounting face to outer edge of outer rim.


Assuming the et30 outboard dimension doesn’t take the wheel rim beyond the rear arch position I cannot see the et30 offset being a problem? However I would advise that folks check the above dimensions on their car, unless of course they happen to be running this 8x17 et30 fitment already.


Hope this helps.

Kind regards

James.(compomotive)

Hope this helps everyone.

[Paulus H]

James was the guy I communicated with when I bought my wheels. A very professional and down to earth guy. He kept me informed weekly as to how my order was progressing. My overall impression of whether I would buy Compos again was helped by James's professionalism. Paul

[JL37]

Thanks Paul for the feedback. Your car looks stunning by the way!

[iVXT]

Thanks Jason for posting all the info & the reply from Compomotive with the measurements. Also thanks siztenboots for your input as well, is it worth having geo settings done after wheels changed even on standard billys or not really needed unless had suspension change? I'm still not sure which would be the ideal offsets for the rears as conflicting opinions but see what you mean about sticking to et35 if that's what was put on vxr. Ideally I would like no rubbing if poss. Would it not be better then to stick with front offset Lotus/Vaux used on vxr as well then or did people just go et20 in case they fit 4 pots later? Cheers guys.

[siztenboots]

if just changing wheels then no need to reset the geo. Pretty much any high street tyre place will give a free alignment check. Take them up on their offer to get the figures as a rough baseline. Then post up the printout. again a 225/45/17 rear wheel is only a guideline size, not an exact measurement, some will rub, others won't. rear clams, I have measured as much difference as 10-20mm side to side, depending on if they are the subframes shims fitted and how well they were adjusted. Worn bushes were partly to blame for rubbing plus R888s are a wide shoulder tyre, on standard suspension you will wear through the liners.

[iVXT]

Ahh the joy of manufacturing tolerances. So if you've seen 10-20mm diff side to side an et30 rear could rub outer arch just like an et35 could rub inner arch. Sounds like might just be luck of draw on each individual car then. Maybe we should stick to last group buy spec then of et20 front & et35 rear sounds a gamble either way? I'll be running the Yoko A048 LTS tyres, not sure how these compare to 888's for shape of tyres. Cheers.

[Pooh Bear]

I thought the VXR speedlines were et30 rear?? (8jx17)

An old group buy thread for wheels <<here>> had done all the ground work over sizing and were copying the VXR speedlines. This group buy never came off but I used the sizing and have wheels in:
Rear: 8jx17 et30
Front: 7jx16 et23

My rear:

No rubbing with Toyo R1's. The tiniest of scrub when using R888's but not enough to make me do anything about it

ETA found another rear pic (a bit naff) but the wider stance of et30 is

Edited by Penny, 04 November 2010 - 11:06 AM.

[iVXT]

Thanks for the post with that link Penny & the nice pics they're a great help. Am I right your car looks to be running lower than standard as well? If that's the case even better if yours hardly catch. Is that without any arch mods as well? So from the link above these are the details said to the same as the vxr speedlines: Front wheels 7 x 16 ET23, 110 5 stud PCD and 65.1 Centre Bore. Rear wheels 8 x 17 ET30, 110 5 stud PCD and 65.1 Centre Bore. PCD is the pitch circle diameter (110mm required on VX's) Centre Bore is the hole that will allow the hub to fit through to get a correct fit. So hopefully that's now the right info for what we should be ordering in the group buy. What do you reckon folks?

[don.hasi]

@Penny: what size have your tires please?

[Pooh Bear]

Yes - lowered (as much as I dare) with GAZ shocks. It is only the O/S/R which catches ever so slightly so I'm guessing a geo will sort it out in the worst case, but haven't even looked at skimming the wheel arch trims which may be all it needs? Tyre sizes: Front 195/50R16 Rear 225/45R17