i need new tires

i need new tires

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Discussion

avance70

Original Poster:

45 posts

196 months

Friday 17th June 2005
quotequote all
ive got renault clio 1.2
and 155/70 R13 tires

so correct me if im wrong:

1)wider tires do:
-improve handling
-improve braking
-degrade acceleration
-degrade top speed
-degrade mpg

2)shorter tires do
-improve acceleration
-improve top speed
-improve mpg
-degrade handling
-degrade braking

so i plan just to get wider tires like say: DUNLOP SP2000 which are 205/50 R13
can i just fit these on my car or do i need some modifications?
are these too wide?

and... any other suggestions?

Mutant Rat

9,939 posts

215 months

Friday 17th June 2005
quotequote all
avance70 said:
ive got renault clio 1.2
and 155/70 R13 tires

so correct me if im wrong:

1)wider tires do:
-improve handling
NO! They mayincrease available grip, if the suspension geometry works with them, but handling and grip are two very different things. Breakaway when the limits of grip are achieved is likely to be more sudden, and you may find that you have less grip in the wet. They will be much heavier, so the increase in unsprung weight may adversely effect both ride and grip
-improve braking
Probably, yes (unless in the wet or icy conditions, in which case probably, but not necessarily).
-degrade acceleration
At high speed, yes; due to increased rolling resistance and inertia. At low speed you have more grip, though, so less wheelspin(assuming you have enough power to spin the wheels, that is. On a Clio 1.2 this probably doesn't apply at any speed over 10mph in the dry).
-degrade top speed
Yes, slightly. Due to increased rolling resistance
-degrade mpg
Yes, due to increased rolling resistance

2)shorter tires do
-improve acceleration
Yes. Reduced rolling circumference effectively lowers the gearing.
-improve top speed
Depends. Lowering the gearing means that the engine is revving higher for a given road speed. Your engine has a rev limiter, so if it is capable of pulling maximum revs in top gear, lower profile tyres (ie. lower overall gearing) will reduce the top speed. A 1.2 Clio will probably not pull maximum revs in 5th, though, so you get into complicated calculations to do with gearing, power peaks, and aerodynamic drag. Or try it and see. Might go faster, might go slower, depending on the above factors.
-improve mpg
Depends, but probably NOT. Lower profile tyres tend to have slightly lower rolling resistance due to less sidewall flex (which is good for fuel consumption), but the smaller diameter lowers the gearing, as described above (VERY bad for fuel consumption). Bit like driving everywhere in 4th instead of 5th...much less fuel efficient.
-degrade handling
Yes, usually. Higher profile tyres tend to give much more progressive and predictable handling. But grip may be increased. In other words, the car may be capable of cornering at a higher speed, but when it finally lets go, it does so more abruptly and less predictably. The lower profile will also degrade ride quality
-degrade braking
No. Braking will usually be improved, because grip is improved. Wheel lock-up may be slightly les predictable, but if you have Anti-Lock brakes, this is more or less irrelevant.

so i plan just to get wider tires like say: DUNLOP SP2000 which are 205/50 R13
can i just fit these on my car or do i need some modifications?
are these too wide?

To get the best from the car, you will also
need different shock absorbers and slightly stiffer springs to cope with the increased unsprung weight of the wheels.

You will obviously need wider wheels (205 tyres are way too wide for any wheel designed to accept 155 section tyres), and these wheels will need to be of the correct offset to work with the suspension geometry.

Suspension geometry may also need to be changed: wider, lower profile tyres are much less tolerant of camber angle (the angle of the tyre to the road surface, which changes as the suspension moves).

You will need to declare the modifications to your insurance company (even it it's just a change of wheel and tyre), otherwise your insurance will technically be invalid, and they will probably whack a big loading on your insurance


and... any other suggestions?
On a 1.2 Clio, I'd be inclined to leave well alone. Renault has spent millions developing and testing your car to give optimum performance with the tyre sizes it came with. Leave it standard and save your money for a more sporty version in the future - If you get a Clio 182, for example, Renault have done the balanced package of bigger wheels/tyres, different springs and dampers and different suspension/steering geometry so that everything is kept in balance. Trying to get the same results yourself on a 1.2 Clio not only requires a lot of knowledge of car handling and set-up, it will probably end up costing you a bundle more money, too.



...just to add, you have my sympathy. I ran a 1.2 Clio as a company car for about 9 months a couple of years ago, and thoroughly horrible it was too! Handling and braking weren't that bad, though - lack of power was by far its worst problem

>> Edited by Mutant Rat on Friday 17th June 21:27

agent006

11,773 posts

234 months

Saturday 18th June 2005
quotequote all
avance70 said:
so correct me if
so i plan just to get wider tires like say: DUNLOP SP2000 which are 205/50 R13


The SP2000 are some of the worst tyres i've ever come across. Overpriced, overmarketed, slippery, noisy and give crap ride. If your'e after grip, look at getting a better tyre in your current size (Goodyear F1, yokohama AVS or their semi-slick range) rather than a bigger repmobile tyre.

avance70

Original Poster:

45 posts

196 months

Saturday 18th June 2005
quotequote all
thanks i just bought "sava" 155/70 R13 (clio 1.2 regular)
picture here : www.reifen.de/sava/effecta_-/155-70_r13_75t.html
i chose this brand because its produced here and its quite cheap... and hey, its a great tire i say!