Mixing Tyres

[revilla]

I have recently had it pointed out to me by Nick Potter that my rear tyres are perished and the inner sidewalls are cracking to the point of being an MOT failure when the time comes around in a month or two.

 

The car has Avon CR500s 195/45 R15 all round. Considering the fact that they are date stamped 2007 they haven't done too badly I guess (I've only had the car for the last year of that myself).

 

For various reasons (and after reading the various threads on here) I was planning to give a set of Toyo R1Rs a try in 195/50 R15 size next time around. My question is, given that only the rears are looking knackered, am I OK to mix CR500s on the front and R1Rs on the rear until the fronts need doing too? When the fronts finally give up the ghost I would then replace them to match the rears.

 

As well as the differences in tyre characteristics, I reckon that the rears being 50% profile instead of 45% will give me about an extra 10mm (5% of 195mm) rake.

When we set the car up we did have difficulty getting the recommended 15mm rake and a decent sump clearance so I think I'm running a bit less anyway, but an extra 10mm will definitely give me more than ideal, but I've no idea how much of a handling impact this will have.

 

The car is likely to be used exclusively on the road rather than the track, so if the handling effects would just be of the "losing a second or two a lap round the track" variety I wouldn't be too concerned, just don't want to end up with dangerous oversteer or similar when driving it enthusiastically on the road.

[Roger Ford]

Paranoid answer: You should never mix tyres. Tyres are designed to work together, and putting different types of tyres on will cause your handling to go to pot, your insurance to be invalid, and you'll probably die horribly in a firey accident.

 

Pragmatic answer: It'll be fine. People mix tyres all the time on tintops, and nobody thinks there's anything odd about putting wider tyres on the back than the front. If it does cause any instability, it should be quite noticable before it dumps you in a ditch. Your insurance company probably aren't interested but there's no harm in letting them know.

 

Take your pick.

 

[dannylt]

It's probably safer in a car like a 7, since you can feel the grip much more easily and it's never going to surprise you. Sounds like you'd just get horrible understeer though, in which case you'll quickly want to swap out the hardened fronts too. I had some 7 year old CR500s too, and they were comically bad!

 

[Andy-M]

pah, that's nothing - I have 15 yr old A021-R's! They are all getting changed shortly though!

[myothercarsa2cv]

Probably still grippier than brand new ZV3s

[DougBaker]

Don't forget that grippy tyres just means you crash at a faster speed.

[Mark Durrant]

Grippy tyres = shorter stopping distance.

 

Personally if the front tyres are also 7 years old I would change all four.

[rgrigsby]

Personally I wouldn't ever mix tyres on seven, even on the road. Ok so yes you should be able to feel what's going on more than in most cars but R1R's and CR500's are very different tyres with different amounts of grip and they will heat up differently as you use them.

 

This could lead to some very strange and potentially dangerous handling characteristics. This may sounds over the top but even running different compounds of the same tyre front and rear can be "interesting".

 

I don't know how much 15" R1R's are but for the sake a few £00' pounds I would just change the whole lot.

 

Cheers

Rob

 

Edited by - rgrigsby on 17 Jun 2013 15:30:12

[Roger Ford]

Quoting rgrigsby: 

they will heat up differently as you use them.

Don't rear tyres generally heat up quite differently from fronts? Does your handling suddenly go to pot if you spin up the rears a few times without braking hard at the front?

[revilla]

OK thanks everyone for the wide range of opinions expressed!

 

I have ordered two for the rears and I will be using it on road only. I will drive cautiously until I know I am comfortable with the way it handles. If it's not nice, I'll buy two more for the front straight away, otherwise I'll use the CR500s on the front until they are shot then switch.

 

Interesting to read that people would expect the grip levels on seven year old CR500s to be shocking due to the rubber hardening - being the only tyres I've ever known on a Caterham (only had it a year) I thought they were nothing short of phenomenal! I'm obviously not pushing it hard enough. I look forward to seeing how it feels with some new rubber.

[Barbarossa.]

If your tyres are lasting 7 years, you need to:

 

- Drive it harder

- Drive it more

- Upgrade your engine

 

And be ashamed of posting about the fact on here!

 

Edited by - Barbarossa. on 18 Jun 2013 12:13:52

[revilla]

@Barbarossa - In my defence, if you read my earlier posts in the thread you will see that I have only had the car for less than a year, so I think the guilt lies largely with the previous owner!

[Barbarossa.]

I'll let you off then. I think that I would change all 4 though. If the rears are getting to the point where the carcass is cracking, the fronts can't be much better.

[skeetsy]

Another option is to stick the new tyres on the front and hoon the life out of the old CR500's on the rear, then get a new pair of TOYO's for the rear to match the front set 😬

 

All the best

 

Richard

[MADMALC]

Just a short anecdote for interest only.

A 7 owner being short of cash at the time fitted ACB10s on one end and AO48rs on the other for a track day. He reported that there were no problems with grip or handling.

This was a very good experienced driver and a L7C Spint champion.

[SV Gary]

I recently had a puncture in one of my rear cr500s just prior to going to IOM TT and so ran Medium Khumo V70s on the rear and Cr500s on the front - it didn't hold me back over the mountain section of the course 😬