Tyres

[dti-dave]

Could someone please lend a hand on tyre selection I am planning to change my original wheels for 7x17's 28 mm offset and I plan to use 215 on the front and 225 on the rear Rims are speed line 11 spoke. Question is what boots to use os2 os3 or F1 has anybody got any experience with the larger rims and tyres? Thanks...

[RCA]

I have 7-17 on mine with 225/45's at the mo, Pirellis all round, excellent grip but have worn them out in 7 weeks!!!!!!, Once suspension is sorted going for a 8-19 wheels. I think SO-2's are v.rare now so it would probably have to be SO-3 if you were to go for Bridgestone. Also highly rated are the Eagle F1's and the Toyo Proxes.

[GreenV8S]

dti-dave said:

Could someone please lend a hand on tyre selection I am planning to change my original wheels for 7x17's 28 mm offset and I plan to use 215 on the front and 225 on the rear Rims are speed line 11 spoke. Question is what boots to use os2 os3 or F1 has anybody got any experience with the larger rims and tyres? Thanks...

Way back when S03pp were new, I remember somebody put a set on 17" or 18" rims and said they were dreadful. I think they're pretty good on 16" rims. They do seem quite a bit stiffer than S02pp and I think you need a decent amount of sidewall height to get compliance.

[19560]

215 and 225 are very close. There is usually a 20mm difference. People usually go for 7 1/2" rims, then fit 235 or 245 at the rear.

[dti-dave]

Why do you need to have 20mm difference between the front and back the wheel size was recommended and the tyre size also recommended and the reason given was that the tyre would not be over stretched on the rim I assume this might give the slightly greater flexibility in the side wall or is my understanding crap

[19560]

The difference is usually 20 or 40 from the factory. One problem with rims is do you want the same width front and rear? If so and you want 215/40/17, then 245/40/17 on the rear with 8" rims would give the correct rolling radius. Alternatively you could fit 205/40 on 7 1/2" and 235/40 on 8 1/2". As for sidewalls either of these options or your original will give a much stiffer sidewall which may skip over uneven roads or be more likely to aquaplane in the wet. I hope that this helps.

[k4trv]

dti-dave said:

Could someone please lend a hand on tyre selection I am planning to change my original wheels for 7x17's 28 mm offset and I plan to use 215 on the front and 225 on the rear Rims are speed line 11 spoke. Question is what boots to use os2 os3 or F1 has anybody got any experience with the larger rims and tyres? Thanks...

Think you need to refer to Bible Mk 2, page 332. A Richard Branch went for 17 inch front and 18 inch rears. Offset on Chimaeras/Griffiths are at least 35 mm. Example in bible ended up with 40mm offset and still needed 6 mm spacer at front and 3 mm rear.

I really think you need to double check your rim offset selection !!

Trev McM

[dti-dave]

Guys thanks for the help my Chimaera is a late 1999 I thought the wheels and brakes came off the 2 ltr Sierra therefore the of set was 28. If as you say 40+ may be needed
Then will the tracking be way off, and then lead onto suspension issues. Would you say changing the wheels is a good idea or is it more trouble than it’s worth. I understand it will give a harder ride and the risk of skipping will be increased.

[19560]

For any of the tyre or wheel sizes mentioned so far there shouldn't be any need to change the offset (which is the distance from the centre of the wheel to the hub bearing.) On the positive side 17" wheels will give you less body roll and are superb on smooth dry roads... I have made a switch from 15" to 17" (not on a Chimp though) but switch back to 15" for Oct to March. Whether it's worth it depends on how and where you use the car and how much money you've got I'd say. An extra set of wheels is always handy.

[davidn]

Try this link for an offset calculator, I used it when changing to 17" rims. I ended up with ET35mm offset on a 7.5" rim all round. An ET of 28mm on front should be okay, std is 25mm but the rear will need to be at least 35mm to avoid needing spacers. http://toy4two.home.mindspring.com/offset.html
Davidn

[Corin Denton]

dti-dave said:

Guys thanks for the help my Chimaera is a late 1999 I thought the wheels and brakes came off the 2 ltr Sierra therefore the of set was 28. If as you say 40+ may be needed Then will the tracking be way off, and then lead onto suspension issues. Would you say changing the wheels is a good idea or is it more trouble than it’s worth. I understand it will give a harder ride and the risk of skipping will be increased. I've set up a couple of Chimaeras on this type of set up. The offsets changed in 1995 on Griffs etc so you need to be careful of that. I personally run 7x17 Kahn RSRs with 2154017 and 2354017 Avon ZZ3s which are fine but if you are buying new tyres there is only one true option now and that has to be the Toyo Proxes T1S. The Bridgestone SO2 was great the SO3 not quite so great but they do have a very stiff sidewall which is why they are favoured for track use but drop the profile down again for 17" use and they become unbearable with tramlining etc. You will notice a difference with ride quality by going to 17" but it's more likely to show any weaknesses in your suspension bushes etc. The Toyo is by far the best tyre I have ever pushed hard. Period. I suppose that is why it is factory fit for all new TVRs now. Just to throw a spanner in the works why don't you consider one of the bargain setups from TVR at the moment..... 4x 16" TVR Spider wheels 4x 16" Toyo tyres 4x 5 stud hubs 4x Tamora four pot calipers 300mm disc conversion rear discs etc. etc All for £1300!!!! Bargain!!

[shpub]

dti-dave said:

Guys thanks for the help my Chimaera is a late 1999 I thought the wheels and brakes came off the 2 ltr Sierra therefore the of set was 28. If as you say 40+ may be needed Then will the tracking be way off, and then lead onto suspension issues. Would you say changing the wheels is a good idea or is it more trouble than it’s worth. I understand it will give a harder ride and the risk of skipping will be increased.

If you want to do it because it looks pretty then go ahead but be very very careful. Some people have had to fit locks on the steering rack to prevent the wheels hitting the body and due to the handbuilt nature of the cars, it is rare for anything to be absolutely square. So check and double check.

Wider wheels with lower profile tyres will control sidewall movement at the expense of a harsher ride, tramlining, regular trips to the dentist to replace fillings but people's tolerance of this varies.

Has very little effect on body roll because that is predominantly due to the spring and anti-roll bar set up but the improved sidewall stiffness will enable faster cornering which will induce more body roll. If anything, the car can be pushed a bit harder and this will result in more roll. A slightly wider wheel is recommended and this would help improve the tyre profile and contact patch but there is not much space to play with so again chcek and double check.

If you want better handling and performance, you would be better off spending the money on improving the suspension with a set of better shocks etc.

Steve
www.tvrbooks.co.uk