offsets again, 9 inch rears
Discussion
Is anyone running 9inch rims on the rear of a Griff ? If so what offsets have you got?
My reasoning is the 7.5 inch rims are ET35 and of the extra 1.5 inches half will be either side. So to be certain of clearing the suspension I have to take 0.75 inches off of the offset which gives an ET of about 14. What I can’t decide is does that move the centre of the tyre out relative to the original. I think it must do. In which case does the wheel arch become a problem.
My reasoning is the 7.5 inch rims are ET35 and of the extra 1.5 inches half will be either side. So to be certain of clearing the suspension I have to take 0.75 inches off of the offset which gives an ET of about 14. What I can’t decide is does that move the centre of the tyre out relative to the original. I think it must do. In which case does the wheel arch become a problem.
Are you assuming the wheels have a negative offset? I couldnt make 14
I would have thought ET35 - (3/4*25) ~= ET16
From Experimentation:
et33 / 8.5J with 18" spider has no clearance prob inboard, but rear is run high/stiff to allow(/&limit) suspension travel to outer bodywork (look at a few cerb wheel arches...)
front et42 (what the hells wrong here moment) was only @3mm short before obstruction (hence guess 8.5J/et33 => @6mm clearance to upright)
If my ready reckoning is right et30 would be tight.
Dave
I would have thought ET35 - (3/4*25) ~= ET16
From Experimentation:
et33 / 8.5J with 18" spider has no clearance prob inboard, but rear is run high/stiff to allow(/&limit) suspension travel to outer bodywork (look at a few cerb wheel arches...)
front et42 (what the hells wrong here moment) was only @3mm short before obstruction (hence guess 8.5J/et33 => @6mm clearance to upright)
If my ready reckoning is right et30 would be tight.
Dave
I must not drink then do sums I must not drink then do sums I must not drink then do sums
Edited by spend on Wednesday 31st January 09:32
How tight are you on the suspension now? Hopefully you can put at least some of the extra width on the inside. You can see how close the tyre is to the body now, and surely if you put 1 1/2" extra all on the outside you're going to hit the bodywork by miles - unless you plan to put some tasteful flared wings on it?
I'm a bit of a numpty on this subject, but I found this www.1010tires.com/WheelOffsetCalculator.asp it helped me understand better what's going on!!!
Paul; that info would be very useful thank you.
Peter; yes that is my concern and no I don’t plan to pop rivet on some arches from a 70’s escort body kit.
Harry; thanks for the link.
Dave ; I assumed that the offset was from the centre line of the wheel and that it starts off with an offset towards the hub side of the wheel. Now even more confused.
I don’t want wider tyres, the 245 is fine. The problem is that 245 or the equivalent slick doesn’t really fit well on the 7.5 rim. Ideally it should be an 8.5 but all I can find are 8 or 9 inch rims and I am told wider is better than narrower.
Peter; yes that is my concern and no I don’t plan to pop rivet on some arches from a 70’s escort body kit.
Harry; thanks for the link.
Dave ; I assumed that the offset was from the centre line of the wheel and that it starts off with an offset towards the hub side of the wheel. Now even more confused.
I don’t want wider tyres, the 245 is fine. The problem is that 245 or the equivalent slick doesn’t really fit well on the 7.5 rim. Ideally it should be an 8.5 but all I can find are 8 or 9 inch rims and I am told wider is better than narrower.
Steve, the ET figure is taken from the centre line of the wheel, so if you want to keep the centre of the tyre in the same place, ie not push the centre line further out or in, then keep teh ET the same.
If you want all the extra wheel on the inside, use 35+half the extra width in mm (19) = ET54
If you want all the extra wheel on the outside, use 35-half the extra width in mm(19) = ET16
As for what would fit best, I have absolutely no idea
Virgil.
If you want all the extra wheel on the inside, use 35+half the extra width in mm (19) = ET54
If you want all the extra wheel on the outside, use 35-half the extra width in mm(19) = ET16
As for what would fit best, I have absolutely no idea
Virgil.
GreenV8S said:
Does beg the question of what you are doing on the front - where packaging is likely to be a lot harder and the inset will be more critical.
Good point. Interested but will hold back on this one. I can't see a problem with my foot print front or rear with a fair bit! of power.
I run 16 x 7.5 rears on the front with 5mm spacer to stop catching the lower wishbone - can't see how a wheel another inch wider regardless of offset will fit.
Does it have the power to really test these tyres or do you just want to be able to go round any corner like it is on rails. Or Bling.
I recon bigger than 7.5 front and 8 maybe 8.5 rear would be max that would fit - have seen 18" Spiders from Cerb - do look good but then have to possibly sort ride height with adjustables............
You need to be able to light them up to........
Does it have the power to really test these tyres or do you just want to be able to go round any corner like it is on rails. Or Bling.
I recon bigger than 7.5 front and 8 maybe 8.5 rear would be max that would fit - have seen 18" Spiders from Cerb - do look good but then have to possibly sort ride height with adjustables............
You need to be able to light them up to........
steve-v8s said:
I thought the front was easier as the recommended width range for the 205 is 7-8 so a 7.5 rim fits the bill, is available and offset ( or inset) if we are calling it that is not far off the original. Would like to know however where Pete got a 8.5 x17 rim from.
With a 9" rim presumably you're looking at somewhere in the region of 250 width tyres on the rear, but still sticking to 205 on the fronts? That seems like a bit of a mismatch.
stevev8s said:
Would like to know however where Pete got a 8.5 x17 rim from.
I believe he is running Azev E's on his.Try www.azev.com Always thought the C's might look ok on a griff.
I'm running 8x18 with 245/35 rubber and a 35mm offset on the rear and 7.5 x 17 with 215/40 rubber with a 30mm offset on the front.The wheels sit almost identically as they did with the original 7x15 and 7.5 x16s.
Also try www.imagewheels.co.uk very knowledgeable about offsets aswell apparently!!
Edited by scorcher on Wednesday 31st January 19:55
jellison said:
I run 16 x 7.5 rears on the front with 5mm spacer to stop catching the lower wishbone - can't see how a wheel another inch wider regardless of offset will fit.
Does it have the power to really test these tyres or do you just want to be able to go round any corner like it is on rails. Or Bling.
I recon bigger than 7.5 front and 8 maybe 8.5 rear would be max that would fit - have seen 18" Spiders from Cerb - do look good but then have to possibly sort ride height with adjustables............
You need to be able to light them up to........
8.5 or 9 inch rims won't clear the wishbones at 16", but maybe at 17" or 18" they will. With bigger wheels the rim will be further away from the wishbone anyway, it being triangulated. The larger the wheel the wider it can be without fouling the wishbone - fouling bodywork will become ths issue instead, especially after you've dropped the suspension to avoid the 4x4 look as you say! Does it have the power to really test these tyres or do you just want to be able to go round any corner like it is on rails. Or Bling.
I recon bigger than 7.5 front and 8 maybe 8.5 rear would be max that would fit - have seen 18" Spiders from Cerb - do look good but then have to possibly sort ride height with adjustables............
You need to be able to light them up to........
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