Better acceleration with 13inch wheels?
Discussion
Hi guys, I'm pondering on the idea of getting some 7x13 inch superlites for my mini but don't want to spend the cash, only to find it makes no difference! I'm running 6x10's with road legal semi slick yoko's at the minute but my problem seems to be traction. I've got a supercharged 150bhp a series under the bonnet and all it wants to do is wheel spin and pull me all over the road, rather than up the road! I know in theory that 13 inch wheels should dull the acceleration but I was just thinking the lager footprint of rubber on the road might be better? I'm taking it to Santa pod next weekend for mini in the park and want to see what it will do the quarter mile in, but I'm worried I'm just going to be sat on the line in a cloud of tyre smoke! The clutch is just like an on/off switch as well so that doesn't really help matters! I do really like Mini's on 10 inch wheels so I would be a bit sorry to see them go, but at the same time I want it to drive the best it can. Any thoughts on what would be best?
To be clear, the change from 10" or 12" to 13" will not alter the gearing by more than a few percent. The 13" tyres are a very low profile so the rolling radius is not much different from the 10".
In dry conditions a larger contact area as provided by the 175 x 13" tyres might give a slight improvement, but in the wet it'll be even worse than with a 165. Remember, a larger contact area on the road will reduce the contact pressure of the tyre to the ground and factors like tyre compound will be very significant.
The problem is the light weight of the car and the fact that there is weight transfer onto the rear with hard acceleration, so the front wheels have less down-load and thus the wheels will spin. A larger contact area may well not help on a smooth track, or indeed anywhere.
For the sort of power you have a limited-slip diff would help, although it does make the car harder to drive on the road and significantly alters the handling characteristics; not necessarily for the better.
In dry conditions a larger contact area as provided by the 175 x 13" tyres might give a slight improvement, but in the wet it'll be even worse than with a 165. Remember, a larger contact area on the road will reduce the contact pressure of the tyre to the ground and factors like tyre compound will be very significant.
The problem is the light weight of the car and the fact that there is weight transfer onto the rear with hard acceleration, so the front wheels have less down-load and thus the wheels will spin. A larger contact area may well not help on a smooth track, or indeed anywhere.
For the sort of power you have a limited-slip diff would help, although it does make the car harder to drive on the road and significantly alters the handling characteristics; not necessarily for the better.
Hi Cooperman, thanks for your thoughts there! I do really like the fact that my mini is on 10's and a set of super lights with yoko A048r is going to be over £600. I could get an LSD for a similar amount of money so do you think that would be a wiser investment? Do you know how an LSD will change the handling characteristics as it pulls all over the road anyway on anything but a flat surface going in a perfect straight line! You can feel the individual wheels spinning up and pulling the car at the minute! I never use my car in the wet, it only comes out on sunny afternoons for b road blasts and I would like to do a couple of track days, so day to day practicality is not an issue. Do you know what type of LSD would be best? I've seen mini sport do quaife, sailsbury and trans x but I don't know the difference? Thanks again!
Maybe it's just me, but over many years of driving Minis in rallying I've never managed to get on with any type of LSD. I'm told they are great for racing but can't really comment.
The first time I tried an LSD was a Salisbury and it was on B-roads in the wet. I couldn't get used to it pulling all over the road and the fact that when I lifted off in a corner instead of tightening into the corner it wanted to go straight on!
My son was co-driver on an event in Belgium and when the car ran wide on a 90 degree corner with the outside wheels going onto the grass, the application of power caused the wheels still on the road to grip and throw the Mini straight into the ditch.
For a straight-line drag, however, an LSD is great.
On a track an LSD may well knock a few seconds off the lap time, but on a 'give & take' twisty road I believe, and it's only a personal view, that a non-LSD will be easier and more 'friendly' to drive and it won't make your arms ache after just a few miles.
I hope this helps.
The first time I tried an LSD was a Salisbury and it was on B-roads in the wet. I couldn't get used to it pulling all over the road and the fact that when I lifted off in a corner instead of tightening into the corner it wanted to go straight on!
My son was co-driver on an event in Belgium and when the car ran wide on a 90 degree corner with the outside wheels going onto the grass, the application of power caused the wheels still on the road to grip and throw the Mini straight into the ditch.
For a straight-line drag, however, an LSD is great.
On a track an LSD may well knock a few seconds off the lap time, but on a 'give & take' twisty road I believe, and it's only a personal view, that a non-LSD will be easier and more 'friendly' to drive and it won't make your arms ache after just a few miles.
I hope this helps.
Cooperman said:
Maybe it's just me, but over many years of driving Minis in rallying I've never managed to get on with any type of LSD. I'm told they are great for racing but can't really comment.
The first time I tried an LSD was a Salisbury and it was on B-roads in the wet. I couldn't get used to it pulling all over the road and the fact that when I lifted off in a corner instead of tightening into the corner it wanted to go straight on!
My son was co-driver on an event in Belgium and when the car ran wide on a 90 degree corner with the outside wheels going onto the grass, the application of power caused the wheels still on the road to grip and throw the Mini straight into the ditch.
For a straight-line drag, however, an LSD is great.
On a track an LSD may well knock a few seconds off the lap time, but on a 'give & take' twisty road I believe, and it's only a personal view, that a non-LSD will be easier and more 'friendly' to drive and it won't make your arms ache after just a few miles.
I hope this helps.
Its not just you Cooperman I have been driving performance Minis since 1963 and I agree with your comments re LSD being a very mixed bunch.The first time I tried an LSD was a Salisbury and it was on B-roads in the wet. I couldn't get used to it pulling all over the road and the fact that when I lifted off in a corner instead of tightening into the corner it wanted to go straight on!
My son was co-driver on an event in Belgium and when the car ran wide on a 90 degree corner with the outside wheels going onto the grass, the application of power caused the wheels still on the road to grip and throw the Mini straight into the ditch.
For a straight-line drag, however, an LSD is great.
On a track an LSD may well knock a few seconds off the lap time, but on a 'give & take' twisty road I believe, and it's only a personal view, that a non-LSD will be easier and more 'friendly' to drive and it won't make your arms ache after just a few miles.
I hope this helps.
Furthermore I personally find really big wheels on classic minis with very low profile tyres a dead loss on public roads. On the track maybe but on today's roads full of speed bumps and potholes a real liability.
The original Mini was a very balanced car. You make alterations at your own peril. There are improvements to be made but its VERY easy to lose the sharpness and light steering of the Mini with really big tyres and low profiles accentuate the choppy ride.
Not a success in my view.
Steffan said:
Its not just you Cooperman I have been driving performance Minis since 1963 and I agree with your comments re LSD being a very mixed bunch.
Furthermore I personally find really big wheels on classic minis with very low profile tyres a dead loss on public roads. On the track maybe but on today's roads full of speed bumps and potholes a real liability.
The original Mini was a very balanced car. You make alterations at your own peril. There are improvements to be made but its VERY easy to lose the sharpness and light steering of the Mini with really big tyres and low profiles accentuate the choppy ride.
Not a success in my view.
We seem to think along the same lines here.Furthermore I personally find really big wheels on classic minis with very low profile tyres a dead loss on public roads. On the track maybe but on today's roads full of speed bumps and potholes a real liability.
The original Mini was a very balanced car. You make alterations at your own peril. There are improvements to be made but its VERY easy to lose the sharpness and light steering of the Mini with really big tyres and low profiles accentuate the choppy ride.
Not a success in my view.
A lot of people don't understand the difference between road-holding and handling and that is where the advantages of different wheels and tyres comes into play.
Road-holding is the cornering force which a certain set-up is able to generate and it's measured in 'G-force'.
Handling is the way the car responds to the dynamic inputs of power to the wheels, steering and braking.
I've driven cars, Minis included, with super-high road-holding, but very poor handling.
A very wide tyre on a smooth road may well give a higher 'G' capability in certain corners, but overall the handling could be poor due to lack of sidewall flexibility, bump-steer, heavy steering or other factors.
The finest handling Mini I think I ever had was a 1963 850 on Michelin 'X' 145/80 x 10 tyres. But it's road-holding was nothing compared to my 1964 Cooper 'S' rally car on 165/70 x 10 Yokohamas in the dry. In fact I think my Cooper 'S' handles at its best on 165/70 x 10 knobbly forest tyres, but the road-holding then is not too good on tarmac.
A few years ago I did a test day for Mini World where 9 historic competition Minis were tested. Peter Horsborough's 1293 'S' was fastes in a straight line with his 649 cam, LSD, 45DCOE Weber, etc. However, my 1293 'S' was much quicker on the twisty and bumpy tarmac 'rally stage' test. In fact, Peter then changed his engine spec to replicate mine (286 cam, SCCR box, 3.9 final drive, Twin H4 carbs, etc.).
I've never run wider than a 165 tyre, although if I wanted to race I would go for sticky wide race slickes for a dry track.
It's all interesting stuff this, isn't it.
It is indeed intersting, very interesting.
I began with Minis in the days of Clive Trickey of Car and Car conversions fame. Outstanding Mini man and lovely fellow tragically died very young.
All your comment re road holding and handling are absolutely correct.
I am currently completing a Cooper with a 1.8 Twin Cam K series turning out 225 brake. I would like to fit Minilites (copies) and stay down at 12 inch wheels but we shall see. Also fettling a Midas and a Cox GTM both of which run modified 1340cc A series engines
Cars with ultra low profile tyres are undriveable in my experience. Certainly not fun to drive. Too niggly, too easily thrown off line, no suppleness or give left in the suspension. Roads are often very poorly surfaced.
On a track maybe OK but for road use? Never.
On the road its not all about absolute grip: the car must maintain a straight line easily, not tramline, handle properly be nimble on the road etc.
I began with Minis in the days of Clive Trickey of Car and Car conversions fame. Outstanding Mini man and lovely fellow tragically died very young.
All your comment re road holding and handling are absolutely correct.
I am currently completing a Cooper with a 1.8 Twin Cam K series turning out 225 brake. I would like to fit Minilites (copies) and stay down at 12 inch wheels but we shall see. Also fettling a Midas and a Cox GTM both of which run modified 1340cc A series engines
Cars with ultra low profile tyres are undriveable in my experience. Certainly not fun to drive. Too niggly, too easily thrown off line, no suppleness or give left in the suspension. Roads are often very poorly surfaced.
On a track maybe OK but for road use? Never.
On the road its not all about absolute grip: the car must maintain a straight line easily, not tramline, handle properly be nimble on the road etc.
Wow, that 1.8 K-engined project sounds very exciting.
Like you, I started competing in Minis in the early 60's and won my first rally championship in 850's in 1963.
What you say about ultra-low-profile tyres is so true. A friend in our village bought a BMW325 with 18" wheels and 235/40 section tyres and told me that it didn't feel good to drive. I let him drive my 325 which has 16" wheels with 205 section width tyres and he was amazed. He sold his 18" wheels on ebay and bought a 16" set like mine. Now he is very happy with it.
How a Mini with its short-travel suspension can be expected to 'drive nicely' on 50% profile tyres when the suspension was designed for 80% or even 85% profile is beyond my engineering understanding. So much of the Mini's ride and handling is due to the ability of the tyre wall to flex and damp.
Like you, I started competing in Minis in the early 60's and won my first rally championship in 850's in 1963.
What you say about ultra-low-profile tyres is so true. A friend in our village bought a BMW325 with 18" wheels and 235/40 section tyres and told me that it didn't feel good to drive. I let him drive my 325 which has 16" wheels with 205 section width tyres and he was amazed. He sold his 18" wheels on ebay and bought a 16" set like mine. Now he is very happy with it.
How a Mini with its short-travel suspension can be expected to 'drive nicely' on 50% profile tyres when the suspension was designed for 80% or even 85% profile is beyond my engineering understanding. So much of the Mini's ride and handling is due to the ability of the tyre wall to flex and damp.
I entirely agree with your comments re big wheels.
I used to be into very powerful Range Rovers had two John Eales engined One Osselli engined various 3.5,4.2 and 4.9 straight Range Rover cars and 2 Supercharged cars.
All wonderful to drive so dominant on the road. Grace Space and POWER absolutely to this day the most exhilarating road cars I have ever driven on motorways and suchlike in traffic. The vision is so good and no one ever stayed in front on me if I was in a hurry the sheer size of the car impresses other users.
All a bit of a challenge on corners height has its own difficulties at speed!!
And therefore not in the same league as the racers I have driven over winding country roads etc which are so nimble and with the odd 500 BHP under 600 Kilos cars I have driven much much quicker in a straight line certainly around 3 seconds which no Range rover can equal they are too heavy.
Spun two RR's twice with big trailers on the back towing racers to and from tracks. Pure luck got away with it. The devil looks after his own!
Ah! the joys of being an Accountant.
To return to the subject trying big wheels on Range Rovers, Toyota Landcruisers etc convinced me that oversize wheels are a waste of space.
Your post re the BMW handling so much better on smaller wheels precisely reflects my experience.
Retirement has reduced my stable but still got nine cars rebuilding three ever changing lots of fun.
Daily driver classic mini cooper 1430 quick car, BMW Mini Cooper S, very quick car, Freelander ES lovely car marred by poor build quality. Freelander averages over 30. Range Rovers` as U drove them lucky to ge 12 MPG.
C'est la vie.
I used to be into very powerful Range Rovers had two John Eales engined One Osselli engined various 3.5,4.2 and 4.9 straight Range Rover cars and 2 Supercharged cars.
All wonderful to drive so dominant on the road. Grace Space and POWER absolutely to this day the most exhilarating road cars I have ever driven on motorways and suchlike in traffic. The vision is so good and no one ever stayed in front on me if I was in a hurry the sheer size of the car impresses other users.
All a bit of a challenge on corners height has its own difficulties at speed!!
And therefore not in the same league as the racers I have driven over winding country roads etc which are so nimble and with the odd 500 BHP under 600 Kilos cars I have driven much much quicker in a straight line certainly around 3 seconds which no Range rover can equal they are too heavy.
Spun two RR's twice with big trailers on the back towing racers to and from tracks. Pure luck got away with it. The devil looks after his own!
Ah! the joys of being an Accountant.
To return to the subject trying big wheels on Range Rovers, Toyota Landcruisers etc convinced me that oversize wheels are a waste of space.
Your post re the BMW handling so much better on smaller wheels precisely reflects my experience.
Retirement has reduced my stable but still got nine cars rebuilding three ever changing lots of fun.
Daily driver classic mini cooper 1430 quick car, BMW Mini Cooper S, very quick car, Freelander ES lovely car marred by poor build quality. Freelander averages over 30. Range Rovers` as U drove them lucky to ge 12 MPG.
C'est la vie.
Thanks for your thoughts there guys! After a fantastic day racing up the strip at Santa Pod yesterday, i came away with a 15.1 @ 96mph. I think i could have got into the 14's but my poor clutch could take no more and started slipping. I was loosing so much time spinning the wheels in first and second gear, but then making it back up again once i got into 3rd. Even if i lost against the other car in time, my terminal speed was normally higher. I've decided after a long conversation with the guys at Swiftune this morning, to purchase as well as a new rally clutch plate and grey diaphragm, one of their Swiftune A.T.B differentials. Apparently they just behave like a normal open diff when you drive the car normally, so you get none of the heavy steering associated with L.S.D's but start working when you really start to push it! Apparently is should help with my torque steer problems as well. It's arriving later this week and i have to take the engine out and split the gearbox to fit it so i won't be fitting it straight away, but i can't wait to see how it drives after! I'll then be able to keep my car running on 10's which is what i really want as well!
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