Another wheel question

[macdeb]

Just gone through other threads but can't seem to find answer. I know this might seem a bit arse about face but. Just fitted 7.5 x 17 [et35] wheels to my Chimaera. Could not get any help at all from wheel suppliers. Been round the block and no clearance problems. What I want to get right though is the question of offset. I know the offset front to rear are different, and I want to make sure the car runs true and not bring about handling/suspension problems, so will make any spacer/hub modifications needed. But, what is needed? Have heard some say same et [around35] all round is fine, but is it? Also, last 100 Griffs have 16's on front and can only guess they are the same as the rears so have same offset. So have I a problem or not? [besides the obvious]

[davidn]

I fitted 17" x 7.5 ET35s all round on my my old Griff. Didn't experience any handling probelms and had it all set up and aligned by Austec who confirmed it was fine. Like you say the later Chims and last Griffs mostly used the larger diameter rear wheel on the front which if I remember correctly were ET37's.
Which wheels did you go for?
Cheers
David

[macdeb]

I went for Ford RS seven spoke. Didn't want anything to 'bling' if you know what I mean, wanted something a bit more subtle. They were on Pistonheads for sale, fitted with Yokohama Parada spec2 tyres. Gets confusing when some say you can and some say you cant. Suspension geometry and set ups are a dark art to me I'm afraid.

[macdeb]

davidn said:

I fitted 17" x 7.5 ET35s all round on my my old Griff. Didn't experience any handling probelms and had it all set up and aligned by Austec who confirmed it was fine. Like you say the later Chims and last Griffs mostly used the larger diameter rear wheel on the front which if I remember correctly were ET37's. Which wheels did you go for? Cheers David

David, just had another thought, would it be right to think that offset should be OK as I've gone for 7.5" wheel at front and not 7". Maybe that's how yours was OK when set up.

[Bomber Denton]

ET35 is too much for the front to be honest, the standard offset is ET18 from memory? The rears are ET37.

The fronts might foul the arches when driven hard, note i am only saying might.

[GarryM]

My wheels have stamped on them ET25 on the front and ET35 on the rear. I haven't measured them though and IIRC Richb measured the rears at ET37!
The "correct" offset depends on the tyre/wheel width and bearing in mind TVR fit 205 and 225 tyres on the front without worrying about offset, I doubt the 10mm difference will matter much. One of the regular track dayers experienced problems with the standard ET25 after fitting Dunlop semi-slicks. Put spare 16" (ET35 rear) rims on the front and all well again.
If it feels right and doesn't foul the bodywork it probably is right.

[davidn]

Okay try this, from 7" ET25mm to:
7.0" ET35mm - inner clearance = 10mm less, wheel will retract 10mm
7.5" ET35mm - inner clearance = 16mm less, outer rim will retract 4mm
7.5" ET25mm - inner clearance = 6mm less, outer rim will standout 6mm more
7.5" ET37mm - inner clearance = 18mm less, outer rim will retract 6mm

So unless TVR made changes to the hubs etc., then fitting the standard 16" ET37mm rears to the front clearence issues are worse then your/my 7.5" ET35mm wheels it just reduces the track by 8mm over the standard 15" wheel. You could fit 4mm spacers to restore this but I didn't.

No clearance issues for me and no adverse handling apart from slight tramlining which I put down to a lower profile tyre.

Cheers
David

[shpub]

The hubs and upright assemblies do vary. Ask anyone who sells brake upgrades and there are odds ones out there. Also don't assume that the bodies are perfectly aligned.... they are not. Also different suspension setups can cause problems as well.

In the end of the day... it is check the wheels fit the individual car I'm afraid. Use previous experience etc by all means but it is not black and white at all.

[macdeb]

Cheers for the help guys, think I'll get alignment checked then go from there. Thanks again, Mac.

[richb]

Agree with what Steve said, my bodywork is about 5mm to one side, measured against teh wheels! Also, of course, if you decide to go for Nitrons or other susoension upgrades you will need to get the eometry set again. Rich...

[M@H]

The thing to bear in mind is that a 7.5" wheel is 190mm.. the clearance issues discussed are with the tyres not the wheels. A 195 tyre on a 7.5" rim will give you less clearance issues than a 205 on a 7" rim. Calculate tyre sizes into your offset and backspace equations and you'll find you can have a different offset, on a larger rim, but with a narrower tyre and effectively no clearance issues over the standard 7" setup.

Cheers,
Matt.

[JR]

GarryM said:

My wheels have stamped on them ET25 on the front and ET35 on the rear. I haven't measured them though and IIRC Richb measured the rears at ET37!

That's odd, standard is 1" front and 1.25" rear which is 25 and 32mm.
Mavdeb, practically I'd fit 5mm spacers at the front (then you'll be close enough all round) and enjoy the car.

[richb]

JR said:

GarryM said: My wheels have stamped on them ET25 on the front and ET35 on the rear. I haven't measured them though and IIRC Richb measured the rears at ET37! That's odd, standard is 1" front and 1.25" rear which is 25 and 32mm.

Not on my '99 Griff 500 it wasn't. As the man says, 25mm front and 37mm rear. Rich...

[JR]

richb said:

JR said: GarryM said: My wheels have stamped on them ET25 on the front and ET35 on the rear. I haven't measured them though and IIRC Richb measured the rears at ET37! That's odd, standard is 1" front and 1.25" rear which is 25 and 32mm. Not on my '99 Griff 500 it wasn't. As the man says, 25mm front and 37mm rear. Rich...

OK, so your measurement is correct and everyone else is wrong, lol
eg

jsr said:

The standard wheels and tyres on my 94 Chimaera are: <br> <br>Front: 205/55x15, 7" rim width, offset ET25; overall height 607 mm <br>Rear: 225/50x16, 7.5" rim width, offset ET33; overall height 631 mm <br>

[schimg]

macdeb said:

Just gone through other threads but can't seem to find answer. I know this might seem a bit arse about face but. Just fitted 7.5 x 17 [et35] wheels to my Chimaera. Could not get any help at all from wheel suppliers. Been round the block and no clearance problems. What I want to get right though is the question of offset. I know the offset front to rear are different, and I want to make sure the car runs true and not bring about handling/suspension problems, so will make any spacer/hub modifications needed. But, what is needed? Have heard some say same et [around35] all round is fine, but is it? Also, last 100 Griffs have 16's on front and can only guess they are the same as the rears so have same offset. So have I a problem or not? [besides the obvious]

Mac,

From reading this thread it sounds like you are there or there abouts...good buy, are you pleased with the result then i.e. looks?

Steve.

[richb]

JR said:

OK, so your measurement is correct and everyone else is wrong

Sorry, I've no idea. If someone else also takes their rims off and measures them with a steel rule etc. then fine. I only offered the comment to help others, I really don't care I know my wheels fit nicely and don't rub. I guess I was about the 2nd or 3rd owner to fit 18" RL7 wheels back in 2000 which is why I took the time and trouble to chat to Neill Anderson and Peninsula etc. Since then loads of people have done it. Perhaps TVR changed the offsets at some time more recently, maybe when they started using 16" wheels at the front? Thoughts/Comments? Rich...

p.s. the real point I was making is that my wheels were stamped ET35 but definitly measured between 37mm to 37.5mm off-set, so you can't trust the stamp. that's all.

p.p.s. I see one of the posts refers to a 225 width rear wheel so that's an older Griff as the 500's have 245 rears so maybe that's the explanation?

>> Edited by richb on Thursday 8th December 22:42

[macdeb]

schimg said:

macdeb said: Just gone through other threads but can't seem to find answer. I know this might seem a bit arse about face but. Just fitted 7.5 x 17 [et35] wheels to my Chimaera. Could not get any help at all from wheel suppliers. Been round the block and no clearance problems. What I want to get right though is the question of offset. I know the offset front to rear are different, and I want to make sure the car runs true and not bring about handling/suspension problems, so will make any spacer/hub modifications needed. But, what is needed? Have heard some say same et [around35] all round is fine, but is it? Also, last 100 Griffs have 16's on front and can only guess they are the same as the rears so have same offset. So have I a problem or not? [besides the obvious] Mac, From reading this thread it sounds like you are there or there abouts...good buy, are you pleased with the result then i.e. looks? Hello Steve bloke, Yeh, looks better. Been round the block and NO clearance issues, but just want it right. you know, don't want niggling doubts when going into a corner etc. Will get it checked for alignment I think, then go from there. Also, got to get to the bottom of the 'ride height' problem at rear. [evident before wheel change] Gratefull for all replies, [didn't want to start a punch up or anything] just that I understand it, but can't quite get my head around it, if that makes sense? Steve.

[M@H]

macdeb said:

Just gone through other threads but can't seem to find answer. I know this might seem a bit arse about face but. Just fitted 7.5 x 17 [et35] wheels to my Chimaera. Could not get any help at all from wheel suppliers.

I should have said earlier, my "track" wheels are 7" x 17" ET35 with 35 profile tyres on.. they seem ok.

[neejah]

On the subject of offset, I believe a lot of confusion over actual and quoted is caused by the measurement points. I believe that it's from the centre of the wheel, but only goes to the inside of the rim bead not the outer face (something difficult to measure with tyres fitted)....I personally wouldn't be too bothered about a couple of mm!

[richb]

neejah said:

On the subject of offset, I believe a lot of confusion over actual and quoted is caused by the measurement points. I believe that it's from the centre of the wheel, but only goes to the inside of the rim bead not the outer face

However if you think about it logically this makes no difference to the result because what you are measuring is the 'difference' between the amount of rim either side of the centre line. It matters not if the rim measures 178mm or 190.5 mm between the faces, what matters is the difference between these two measurements relative to the position of the machined face at the centre of back of the wheel. Try drawing it on a piece of paper, if you have a 35mm offset it will still be 35mm regardless of the notional rim width. Rich...