Wider tyres in front on a FWD car?
Discussion
I've got a FWD turbocharged car with 8x17" wheels fitted. I've been running 225/35ZR17 tyres till now but am contemplating using 235/40ZR17s at the front, whilst retaining the 225/35 tyres at the rear. The car has coilovers on all 4 corners (height and damping adjustable; fitted with progressive springs 275-400lb front, 175-275lb rear) so I am hoping to work the suspension around the proposed setup to get the best balance possible. Apart from the obvious issue of rolling radius and its effect on the speedo etc., is there anything else which would deem my proposed setup to be counterproductive or dangerous in any way? I am hoping to have improved traction with the 235 tyres at the front but suspect that it may not be all that simple. Any ideas or advice anyone? Thanks.
Edited by t4rrr on Friday 10th November 17:11
There's no reason, in theory, why it couldn't be make to work if - as you say - the rest of the suspension set-up is optimised to suit. Expect some fairly fundamental changes, though, and by the time you have finished juggling all the other factors, you will probably end up with a similar balance as could have been achieved by more conventional means.
In particular, you will end up having to maintain a similar balance of front:rear grip if you want to avoid the potential for fairly vicious lift-off oversteer.
There are reasons why FWD cars are set up to understeer quite heavily, and it's not all down to the front tyres being overworked by having to cope with both drive and steering duties.
In particular, you will end up having to maintain a similar balance of front:rear grip if you want to avoid the potential for fairly vicious lift-off oversteer.
There are reasons why FWD cars are set up to understeer quite heavily, and it's not all down to the front tyres being overworked by having to cope with both drive and steering duties.
Edited by Sam_68 on Saturday 11th November 13:24
The larger diameter on the front may cause clearance issues with arches, suspension and steering components
The larger width on the front may cause more traction issues in the wet (torque steer v aquaplaning). Having said that a 225/35 probably puts a bigger footprint on the road tham a 235/40 anyway! As you lower the sidewall you get more footprint.
Personally I would get a professional to drive your car and give an honest opinion, someone like a motor-racing driver or advanced high performance instructor. The money you'll spend with them will be more than saved in the long run.
It may be the car thats at fault or your driving style, someone 'in the know' driving it would sort that out.
davidy
The larger width on the front may cause more traction issues in the wet (torque steer v aquaplaning). Having said that a 225/35 probably puts a bigger footprint on the road tham a 235/40 anyway! As you lower the sidewall you get more footprint.
Personally I would get a professional to drive your car and give an honest opinion, someone like a motor-racing driver or advanced high performance instructor. The money you'll spend with them will be more than saved in the long run.
It may be the car thats at fault or your driving style, someone 'in the know' driving it would sort that out.
davidy
Edited by davidy on Saturday 11th November 13:18
Thanks for all the replies. I think getting a professional / race driver's advice is actually a very good idea so that I don't end up throwing money at something which is counterproductive. However, can I assume that there's nothing fundamentally wrong with having slightly wider tyres at the front in a FWD car? When I went to have the wheel alignment checked, the tyre company (who are quite well established in the South-West) guys were saying that I should not do that and that its dangerous and not recommended etc. I guess they're more concerned with sudden oversteer or the like, but as already mentioned, I thought there are instances where narrower tyres with shorter sidewalls actually have an overall larger contact patch. Having said that, it might just be due to the fact that I've got Falken FK451s on the rear and they were trying to sell me a pair of Michelin Pilot Sports to replace them! 
combemarshal said:
Can you not just try adjusting the suspension first, Most tin top race series don't allow different size front and rear, and they can get theirs to handle!
Yeah, the whole idea of me fitting the adjustable coilovers was for that reason; I guess I've just not set it up correctly and may need to play around with it a little bit more.
Noticed that you're a marshall at C. Combe, next season, pop & say hi to me in the Med Centre; assuming I'm not out in the car that is!!
Sam_68 said:
Sorry...didn't realise it was a road legal car we were talking about.
In that case, you need to consider the fact that no insurance company is likely to honour any claim made in the event of an accident.
DON'T DO IT!!
In that case, you need to consider the fact that no insurance company is likely to honour any claim made in the event of an accident.
DON'T DO IT!!
apart from the insurance companies and obvious handling problems it's also illegal to have larger tyres on the front - always large rear, small front
the most grip must always be at the rear
t4rrr said:
combemarshal said:
Can you not just try adjusting the suspension first, Most tin top race series don't allow different size front and rear, and they can get theirs to handle!
Yeah, the whole idea of me fitting the adjustable coilovers was for that reason; I guess I've just not set it up correctly and may need to play around with it a little bit more.
Noticed that you're a marshall at C. Combe, next season, pop & say hi to me in the Med Centre; assuming I'm not out in the car that is!!
If it's a track day you'll find me in the pits (yup, Pitts in the Pits!!)
Many years ago when i was a lad we use to fit much wider tyres on the front of our grass track mini's. Anything upto 13inches, very low profile, and very wide with almost slick tread, and standard tyres/rims on the back. We ran LSD's too, which used to break lots so we always had extra spares. It didn't matter how quick you entered the bend, you exited as quickly but those mini's were stripped out and weighed bugger all so they handled like Scalextric cars. You don't see many, if any, FWD road cars with wider tyres up front.
Calorus said:
Why would it be illeagal? Or dangerous?
I'm trying to think of what it was in (this is before TRC) but one of the successfull VW Lupo's had exactly that.
It makes coplete logical sense and allows the suspension to be relatively neutrally tuned, giving you complete control.
I'm trying to think of what it was in (this is before TRC) but one of the successfull VW Lupo's had exactly that.
It makes coplete logical sense and allows the suspension to be relatively neutrally tuned, giving you complete control.
Deliberately by design all domestic cars under-steer. Changes in the pneumatics could belay this safety protocol, so for legal and safety reasons a correct pneumatic footprint is wise.
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