17 replies to this topic

[dasupersprint]

Hello...

 

I have local Mini people here who tell me I should get a 1275 because my 998 won't be up to the task of keeping up with traffic, especially with my 13 inches wheels.

 

I'm just about to rebuild my 998. If I could find a 1275, of course I would do it, but chances are that I will keep the 998.

 

What do you guys think about that? I'm sure some of you are in this situation

[nicklouse]

but why would you want 13s? worse ride and they do reduce your top speed. but your 998 will be fine. but i would put 10s on it.

[dasupersprint]

Thanks but we are not here to discuss wheel choice thanks

[mab01uk]

998 will be fine for keeping up with modern traffic, they are smoother and more robust than the long stroke 1275 anyway, if you still want more the 998 can easily be tuned and modified to at least equal a standard 1275 performance. 13" wheels will also be fine with 998 although as said they spoil the handling of the Mini compared to 10 or 12" wheels but your choice and of course many like the look of 13". You must however fit front disc brakes as drum brakes are not good with13" wheels see below.....

 

Wheels & Tyres - Bigger wheel fitment consideration

By Keith Calver (Minispares Blog)

"This larger 13" tyre footprint-induced grip/drag increase will help with braking, but only if the brakes are equal to the task. The wheel diameter also gives a greater ('longer') leverage working against the brakes. The combined larger footprint and greater leverage means fitting 13-inchers to a drum-braked Mini is an absolute no-no. They simply over-come the applied friction capability of the shoes. Disc brakes are a must. Even the 7.5-inch S type discs are a little marginal in my opinion/experience unless steps are taken to maximise their performance envelope. The 13-inch combination is a good deal heavier in most instances than the standard set-up so up-rated dampers are an absolute must."

https://www.calverst...-consideration/

Edited by mab01uk, 28 September 2018 - 07:34 PM.

[Ivor Badger]

It the outer tyre diameter is the same and it is usually pretty close. Then what does the wheel rim diameter have to do with anything? Saying that, stick with 10" and make it drive like a Mini.

[cal844]

Wheel diameter and width change the gearing, rolling resistance and handling ?

[Ivor Badger]

Wheel diameter and width change the gearing, rolling resistance and handling

 

Yes, we know. tyre diameters, please understand I had to do this on paper, need to buy a new calculator

 !65/70x10 and 145x10 = 485mm

145/70x12  =  507 mm

175/50 x13  = 505 mm

So we are not talking vast differences for a road car.

[timmy850]

I found on my cars that the weight of the wheel/tyre makes more of a difference than the diameter of the rims. I changed from heavy steel 10" wheels to lightweight alloy 10" wheels on my mini and it made a huge improvement to both acceleration and the steering feel. 

 

That said I can just keep with traffic in my 998 with 3 people in the car. I can just image how slow an 850 packed full of people and luggage would be..

 

I changed from 15" wheels to 18" wheels on my Mazda (same overall rolling diameter) and they were significantly more heavy on each corner. You could tell this blunted the acceleration (and also reduced fuel economy)

[KTS]

i don't think you need to change the engine if running 13" rims, but as the Calver article above advises you do need to be running disk brakes

[sledgehammer]

Some 12 inch tyres have a larger radius than a 13 inch ones at a lower profile (which is required for a 13 inch mini wheel)

so engine should be fine , if all is well - maybe go to stage one ?

 

as said above brakes & sometimes dampers need upgrade if heavier wheels

you may need to raise suspension / cut arches

 

also you will sometimes find the steering to be very heavy on sticky profiles at stand still

I did it years ago - regretted it straight away as I felt every tiny bump ,

but it's your car - do what you want

[Ethel]

I suppose when you brake and transfer more of the weight to the front axle, more sidewall means the tyres can compress more reducing the rolling radius. The difference must be marginal and easily offset by other factors - such as 50 profile tyres being intended as performance items so likely a softer and stickier compound. The contact area should also be much the same if you have the same weight of car compressing tyres pumped up to the same pressure. 

[Spider]

There's a good many 998 Big Wheel Mokes out there, all on 13's but not them low profile types, these are all 80 series Weathermaster Tyres (originally). These have a rolling diameter of around 620 mm. These were all fitted up with a final drive of 4.2:1, however, I'll also point out, these give the same road speed as a 3.44 on 10's - 16 mph per 1000 engine RPM in top gear.

 

What it will come down to is a sensible choice of final drive ratio.

[Ivor Badger]

Were bot Australian mokes, where iirc production ended up, built with 13" wheels?

[Vipernoir]

Other than the steering being harder to turn at a standstill and ride quality, most people can't tell the difference between 10", 12", and 13" wheels while driving the car - the difference in rolling radius is insignificant.

 

Like so many subjective things when expressing an opinion, everyone has a different idea of what is acceptable based on individual driving style.

[Aaron3]

I’m running 13’s on my 998 it’s quite nippy for the engine size and is fine keeping up with modern day traffic.
The only mod I’m running is a stage 1 kit, it pulls away nicely at traffic lights and will cruise all day at 70mph.
I think you’ve been told a load of twoddle and in my opinion wheel size is irrelevant to engine size.