tyre question

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ssray
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tyre question

Post by ssray » Wed Dec 14, 2005 10:45 pm

i have a 1.9na bx estate, new tyres v soon, is it worth putting on a wider front tyre than on the rear? i`m thinking of 185/60/14 fr and 165 or 175 on the rear, i have spotted a 1.9 205git with 2 alloys at the local breaker not sure how much(good shoes on) but that would be 195/50/15 and smaller on the rear. i dont seem to get a lot of grip from my 165`s at the mo and the advisory on my mot helps. :twisted:
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Philip Chidlow
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Post by Philip Chidlow » Wed Dec 14, 2005 11:43 pm

I would try and get 16v alloys with 195/60 14's all round. Prefer Pirelli P6000s myself (and not only because they're excellent value for money).

I think it most certainly isn't advisable to put 185's on the front and 165's on the rear and I would have thought putting 15's front and 14's back is a recipe for disaster.
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Post by tim leech » Wed Dec 14, 2005 11:59 pm

Agreed! have the same size wheels and tyres all round.

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cavmad
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Re: tyre question

Post by cavmad » Thu Dec 15, 2005 7:12 am

ssray wrote:i have a 1.9na bx estate, new tyres v soon, is it worth putting on a wider front tyre than on the rear? i`m thinking of 185/60/14 fr and 165 or 175 on the rear, i have spotted a 1.9 205git with 2 alloys at the local breaker not sure how much(good shoes on) but that would be 195/50/15 and smaller on the rear. i dont seem to get a lot of grip from my 165`s at the mo and the advisory on my mot helps. :twisted:
cheers
Ray
No, no and definately no! I wouldn`t like to think what it would do to the handling and if you had an accident (God forbid) you would find that the insurers and the police would have something to say about it I can assure you. Also if you get a puncture how many spares are you going to carry? One of each size? If you don`t mate and end up mixing on one axle you`re really asking for handling and legal problems.
I run 175-70-14`s on my estate (1.9 n/a) and haven`t found any real problems yet. Some people say that running 185/196 60 series tyres on estates can cause the tyre to be a bit close for comfort on the back, so how about (if you can find some) some 175-60-14`s? Not quite as wide as 185 or 195`s but a bit more grip.
Definately don`t go for wider front than rears though mate, really not worth risking it.
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sleepy0905
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Post by sleepy0905 » Thu Dec 15, 2005 7:52 am

I found that my 165`s were struggling for grip but since fitting 16V alloys with 195/60/14 tyres they are excellent they grip like sh*t to a baby`s nappy so i would recomend this way of increasing the wheel and tyre size. :D :D
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Post by tim leech » Thu Dec 15, 2005 9:05 am

Did the same with mine sleepy as you know and its much better, also I chaned the steel wheels on my 19tzd n/a for the wider 185 gti wheel/tyre, much better grip but looks standard as the original trims are back on! Will need new tyres soon as there cheap ones that are a bit worn. I can get 195/60s 14s to fit and they cost me £25 a corner!
Last edited by tim leech on Thu Dec 15, 2005 5:25 pm, edited 1 time in total.

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Post by Cornishbx16v » Thu Dec 15, 2005 12:44 pm

the basis of stability you should have slightly wider tyres on the rear of the car to the front, hence why all supercars have much larger rears than fronts!
It wont be at all safe! the back end will become very loose in the bends due to the lesser amount of tread in direct contact with the road surface!
Your best bet is as many have said, source a set of alloys for the car! the pug 1.9 gti wheels should fit under the arches at the back(??) i know they do on a saloon! but if you can get a set of gti/16v wheels you will notice the difference!
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Post by Oscar » Thu Dec 15, 2005 12:52 pm

Absolutely agree. Don't mix sizes as you will run into legal problems, and if you want to improve handling, get some alloys and run wide tyres. My alloys are so recent that I am still surprised at the difference in handling: more stable, more precise all over.
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cauchoiskev
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Post by cauchoiskev » Thu Dec 15, 2005 5:10 pm

Maybe one of you gents could explain to me something I have never quite understood : why do wider tyres give better grip ? Since, for a given load, and a given tyre pressure, the contact surface should be exactly the same, whatever the width of the tyre... :roll:

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DavidRutherford
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Post by DavidRutherford » Thu Dec 15, 2005 5:15 pm

They don't.

What they usually do have, however, is a lower profile sidewall, which flexes less under cornering, giving you the impression of better roadholding.

What they do have is a larger contact area, which is why a larger heavier cars generally have larger tyres; to maintain the same ground pressure. If you fit wider tyres to a car, you reduce the ground pressure, and run a greater risk of aquaplaning. This can be partially avoided by running with higher tyre pressures. This in turn makes the sidewalls flex even less, and gives an even better feeling of roadholding... at the cost of extra noise and vibration.
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Post by jeremy » Thu Dec 15, 2005 6:53 pm

Just to confuse things - didn't the early CX have larger front tyres than back ones?

I always thought that Supercars had larger back tyres for traction reasons - as they are rear wheel drive. I know that if you go back to the 60's V rated (150 MPH) tyres were best avoided as they were so hard they wouldn't grip in the wet.

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Post by DavidRutherford » Thu Dec 15, 2005 7:07 pm

jeremy wrote:Just to confuse things - didn't the early CX have larger front tyres than back ones?
I don't think so... although the rear wheel cover might well have made it look like that!
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Post by ken newbold » Thu Dec 15, 2005 8:01 pm

If you fit lower profile tyres it will affect the ride quality.

I read somewhere that Citroen designed the BX suspension to run with Michelin 165x70x14's. The Michelin tyre with it's soft sidewall reacts and flex's with the suspension to give the best ride quality.

Think it was in the Citroenian some time ago when there was much debate on tyre useage, best ride, mileage, value etc.
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cavmad
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Post by cavmad » Thu Dec 15, 2005 8:16 pm

The only thing I remember from my tyre fitting days about CX`s was that some had those bloody awful directional tyres on them which started with a wide grove on one side gradually thinning out to one about a tenth in size of a nat`s cock.
If it`s tyres you`re after Mr SSRay give me a shout-I have loads here on BX wheels ready to go straight on and all very cheap.
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Post by mnde » Thu Dec 15, 2005 11:02 pm

Width is neither here nor there... it's what you do with it that counts... ;)

What I mean is, look at the skinny 135s on a 2CV and 145s on a GS, and they corner on rails! With good quality tyres that is! It's how the tread is presented to the road that counts, and with the 2CV and GS it is suspension geometry and dynamics that achieves maximum tread area contact/pressure at all times.

These people who are saying their 165s are strugging for grip at the front. What brand are these tyres, how many mm of tread and what pressure are you running them at?

Naturally the BX suspension was designed to work in harmony with the Michelin tyre, just as with the GS.

I swapped my Firestones at the front (on the GSA), which struggled for grip and wore very fast, for a pair of nearly new Mabors I bought at a rally (sadly no longer available it seems). The handling was transformed! Much more grip, lighter steering.

So before trying to cure a grip problem by going for wider tyres, which could end up making the handling/driving experience worse (aquaplaning, harsher ride etc.), try a different brand of tyre! :)

Also, consider what the optimum pressure is for the Michelin tyre, may not be suitable for other makes. Citroen give 27F / 28R (psi) as recommended pressure for the Michelins on a GS, which works because of its flexible sidewall and makes for a more comfortable ride. But I found 27 seemed far too low for the Firestone tyres I used at the front - the outer edge wore very quickly and I ended up getting braiding poking through on the first set I had!

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