Tyres 205 or 225 for non PAS?
Discussion
Hi , I have a client wanting to change all four tyres on his 99 non-PAS 450 Chimaera , at present he is running S03s but fancies changing to Toyo Proxes , only problem is that Toyo don't manufacture the Proxes in a 205 for the front only the 225 , has anyone upgraded to 225 on their non-PAS car and does it make a noticeable difference in making the steering heavier etc. ? Thanks , Corin.
corin denton said: Spoke to Toyo today , no date of any product availability.
Not surprised... Unless they are making a completely new tyre I can't see how they are going to do this at all. If they do, can't see how this is financially viable. What is wrong with So3s? Rather an excellent tyre in my humble opinion.
Wouldn't recommend a 225 as it does make the steering a lot heavier and put more strain on the components.
Steve
www.tvrbooks.co.uk
I'm running Toyo's all round on my non-PAS Chim. 205/50VR15 front, 225/50ZR16 rear. So the fronts are only speed rated to 149mph. Big wow! Just tell your insurer and there's no prob.
Having previously run S02's all round, I'd say the Proxes T1-S's are even better - especially in the wet. They do go off a bit when a bit worn though
Having previously run S02's all round, I'd say the Proxes T1-S's are even better - especially in the wet. They do go off a bit when a bit worn though
trackdemon said: I'm running Toyo's all round on my non-PAS Chim. 205/50VR15 front, 225/50ZR16 rear. So the fronts are only speed rated to 149mph. Big wow! Just tell your insurer and there's no prob.
Having previously run S02's all round, I'd say the Proxes T1-S's are even better - especially in the wet. They do go off a bit when a bit worn though
The problem is not as simple as that. There is European legislation that states that any replacement part must be as good (or better) as the same spec as the OEM fits. In continental Europe, this is further strengthened by explicitly making it illegal and an offence (on the spot fine I believe). In the UK, it is against the regs but unclear what the repercussions are. At the moment it is a self policing thing but I believe that this will change and we will fall into line with Europe pretty soon as it is a major safety issue.
shpub said:
....as it is a major safety issue.
How? Why? I will never drive over 149mph, so I don't understand this. Why should it be dangerous for me to drive at say 85mph on V rated fronts, but by implication it is not dangerous for a car in front to do the same on H rated tyres if they are OEM spec?
The speed rating is based on the tyres ability to cope with heating. The faster the speed the more heat generated and it is this that destroys the tyre/tread.
Heat is also generated by tread movement which in turn is caused not only by speed but acceleration and cornering. So a lower speed rated tyre has less resistence to cornering and acceleration which means that it is quite possible to overheat a tyre without getting it anywhere near its maximum speed rating. In practice the hotter the tyre the lower the speed rating is before the tread starts sloughing off the tyre which can result in a blow out.
The other problem is that the accelaeration and cornering will also start to distort the contact patch and tyre rolling starts to occur where the sidewalls start to roll over the rim. If the sidewalls are stiffer this is reduced and also the heat resistence is improved and guess what the speed rating is increased.
So you may not be doing 149 mph but you are accelaertaing, braking and cornering hard and on a track day, you are getting near 130-140 mph. What this means is that the limit or safety margin of the tyre is greatly reduced. Even more so on hot days!
In summary, the main concern is with the tyres ability to corner and accelerate as well as top speed.
Heat is also generated by tread movement which in turn is caused not only by speed but acceleration and cornering. So a lower speed rated tyre has less resistence to cornering and acceleration which means that it is quite possible to overheat a tyre without getting it anywhere near its maximum speed rating. In practice the hotter the tyre the lower the speed rating is before the tread starts sloughing off the tyre which can result in a blow out.
The other problem is that the accelaeration and cornering will also start to distort the contact patch and tyre rolling starts to occur where the sidewalls start to roll over the rim. If the sidewalls are stiffer this is reduced and also the heat resistence is improved and guess what the speed rating is increased.
So you may not be doing 149 mph but you are accelaertaing, braking and cornering hard and on a track day, you are getting near 130-140 mph. What this means is that the limit or safety margin of the tyre is greatly reduced. Even more so on hot days!
In summary, the main concern is with the tyres ability to corner and accelerate as well as top speed.
What is this european legislation Steve? And which British regs are you referring to? I don't ever remember you providing any information about any, or is it just something someone told you in a pub?
British legislation requires that you fit tyres suitable for the vehicle and the use to which it is being put. Many people who drive TVRs won't experience tread distortion or overheating or any other tyre problems with V-rated tyres. Some people don't abuse cars the way you say that you do.
British legislation requires that you fit tyres suitable for the vehicle and the use to which it is being put. Many people who drive TVRs won't experience tread distortion or overheating or any other tyre problems with V-rated tyres. Some people don't abuse cars the way you say that you do.
I have mentioned it before. Suggest you spend some time looking at tyre, SVA and OEM replacement of parts legislation if you want details. The tyre thing is part of the same regs that do not permit you to open brake pad boxes, sell non E approved mirrors, lights and tyres and so on. The tyre manufacturers themselves also state the recommendation about speed ratings and look at some European sites and they will say this is mandatory.
The UK position states that the tyres must have a speed rating that is suitable for the purpose. Open to interpretation. Does this mean that if you are doing 50 mph you could use a 70mph remould on a 200mph Tuscan R? Open the throttle and you could shred the tyre. You haven't gone above the speed limit but the tire is clearly not fit for purpose.
This statement is open to big interpretation and as the car manufacturer and tyre suppliers all say the same or better. This is a powerful argument to say they are not suitable for purpose. This ambiguity doesn't exist in Germany, France and so there are moves to harmonise.
Anyway you can go search and look this stuff up. As for V rated being fine... I know some TVR owners don't take their cars out and drive above 30 mph but the majority do enjoy the performance. Tyres are safety critical issues. Why skimp on them and go for a tyre that does need the manufacturers recommendation. You wouldn't go fit a smaller brake pad so why compromise on tyres? Toyo even admit that they do not make a suitable replacement for the 15 inch wheels which is why they are trying to do something about it. So doesn't that tell you something....
If the manufacturer fits ZR or whatever tyres then those are the ones that should be fitted as the car is capable of that performance. As I have explained, it is not necessarily the speed that causes a problem but the cornering, braking and acceleration forces which most TVR drivers do enjoy.
>> Edited by shpub on Tuesday 29th April 14:10
The UK position states that the tyres must have a speed rating that is suitable for the purpose. Open to interpretation. Does this mean that if you are doing 50 mph you could use a 70mph remould on a 200mph Tuscan R? Open the throttle and you could shred the tyre. You haven't gone above the speed limit but the tire is clearly not fit for purpose.
This statement is open to big interpretation and as the car manufacturer and tyre suppliers all say the same or better. This is a powerful argument to say they are not suitable for purpose. This ambiguity doesn't exist in Germany, France and so there are moves to harmonise.
Anyway you can go search and look this stuff up. As for V rated being fine... I know some TVR owners don't take their cars out and drive above 30 mph but the majority do enjoy the performance. Tyres are safety critical issues. Why skimp on them and go for a tyre that does need the manufacturers recommendation. You wouldn't go fit a smaller brake pad so why compromise on tyres? Toyo even admit that they do not make a suitable replacement for the 15 inch wheels which is why they are trying to do something about it. So doesn't that tell you something....
If the manufacturer fits ZR or whatever tyres then those are the ones that should be fitted as the car is capable of that performance. As I have explained, it is not necessarily the speed that causes a problem but the cornering, braking and acceleration forces which most TVR drivers do enjoy.
>> Edited by shpub on Tuesday 29th April 14:10
shpub said: The speed rating is based on the tyres ability to cope with heating. The faster the speed the more heat generated and it is this that destroys the tyre/tread.
Heating may be a factor but the speed rating is actually set by the centrifugal force that the tyre can handle before it rips itself apart.
I expect that you can actually achieve 150+ mph with the rear wheels if you wheelspin it hard in 4th !!!
Matt
Something noone has mention in all this talk of tyre ratings is tram lining. I find this to be abit of a problem in my non-PAS Griff. It depends on road surface etc but on badly worn roads it can be a real handful even with the standard 205's I've got fitted. I would hate to try it with 225's.
Going back to the tyre rating stuff. It is complex but the car and tyre manufactures don't recommend levels for cars for fun. They do it for very good safety reasons. As this is one of the most critical components for keeping your car safely on the black stuff (road - not that travesty of a stout, Guiness) I would think long and hard about ignoring their advice.
Isn't this also covered in the "construction and use" regulations. At the moment, as shpub as said, there is no actual legal enforcement of this in the UK and "you fit at your own risk" but this is likely to change.
At the end of the day it's (at the moment) your choice and you could put re-moulds on BUT is it worth the risk? That is something only you can answer.
Going back to the tyre rating stuff. It is complex but the car and tyre manufactures don't recommend levels for cars for fun. They do it for very good safety reasons. As this is one of the most critical components for keeping your car safely on the black stuff (road - not that travesty of a stout, Guiness
) I would think long and hard about ignoring their advice. Isn't this also covered in the "construction and use" regulations. At the moment, as shpub as said, there is no actual legal enforcement of this in the UK and "you fit at your own risk" but this is likely to change.
At the end of the day it's (at the moment) your choice and you could put re-moulds on BUT is it worth the risk? That is something only you can answer.
OK so if shpub hasn't got a clue he should say so. If you can name the legislation fine but looking for something that doesn't exist is a fools game. (Overtones of Iraq?)
Mnaufacturers of cars and tyres give best advice which is generally superior to the legal minimum. As for OEM you suggest W and Y rated tyres which have an upper speed limit whereas Z rated tyres do not. Or are shpub variations acceptable in shpub law even if contradictory?
Mnaufacturers of cars and tyres give best advice which is generally superior to the legal minimum. As for OEM you suggest W and Y rated tyres which have an upper speed limit whereas Z rated tyres do not. Or are shpub variations acceptable in shpub law even if contradictory?
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