[J1JPE]

I am planning to do a track day in my R56 Cooper which has OEM 16" R94 Bridge-spoke ET48 20.9lb (9.5kg) alloys

http://www.mini2.com/galleries/data/572/R94.jpg

with Dunlop SP Sport 01 DSST RF tyres fitted for daily road use

I also have a spare set of 15" R81 7-hole (aka Imola) ET45 12.0lb (5.45kg) alloys

http://www.mini2.com/qt/r81_silver_wheel.mov

fitted with Pirelli P3000 Energy non-RF tyres

I fancy using the 15s because:

- saves tyre wear on the daily use tyres
- lighter weight of 15s wud mean better acceleration / speeds
- non RFs would corner more progressively than RFs ?
- smaller 15s cud give lower centre of gravity & so improve handling ?

BUT, am concerned about the tracking, wheel alignment being set up for 16s and causing handling problems if I drive on the 15s ...


Am I better swapping to the 15's or keeping the 16's on ?
probably take both a do a few laps on each to find the answer but appreciate people's advice ...

[MINIAC]

If you're going with the 15" wheels you need proper size tires ... 205/55-15.

[NeuroBeaker]

I've got those same 7-hole wheels... the stock tyre size for these wheels is 175/65/15.

An alternative equivalent tyre size to the aforementioned 205/55/15 could be 195/60/15.

15's are a bit of a pain due to the limited availability/choice of performance tyres. Insurance companies (at least MINI Cover, i.e. UK Insurance Ltd) don't seem to understand tyre equivalence and won't let you run on anything except the stock standard BMW-approved 175/65/15 with a choice of either: Dunlop Sport 01 (terrible in cold and wet, I hear... this worries me.) or Pirelli P3000E (I have these, not satisfied with performance or wear).

Would really like to use tyre equivalence to get a set of Goodyear Eagle F1 DS-G3 tyres, or Michelin Pilot Exalto PE2 tyres - but insurance is a killjoy.

[MINIAC]

Quote: Originally Posted by ARCrawford (original)

... insurance is a killjoy.

Don't think they be pleased about the owner doing track days either

[NeuroBeaker]

Actually, I asked Mini Cover about that.

My position was, I wanted to trackday the car but that I was going to take out separate trackday insurance from the venue. Therefore, Mini Cover would only be responsible for insuring the car on the way to and from the track, but not whilst it was actually there. I thought this was fairly reasonable.

Unfortunately, Mini Cover are a bunch of sour-pusses and said that if I was to trackday the car then I would invalidate my insurance for the remainder of the policy. So I haven't had the pleasure of my own car out on the track yet... combine this with the fact that Mini cover told me one thing before I fitted my Koni FSD shocks (i.e. "no Sir, your policy won't be affected in any way. There's no premium increase and your voluntary excess remains unchanged. Simply notify us when the change has taken place and we'll send you an updated cover note.") and then something completely different once they were actually fitted (i.e. "Oh Sir, that's a significant performance increase - we're going to have to adjust your policy... premiums and excesses will need to increase!").

So there are many reasons I won't be renewing with them come March. Their killjoy behaviour and dishonest practices being key here.

But I think I might be getting a little off-topic here, so I'll quiet down for now.

All the best,
Andrew.

[bob corbishley]

Your normal road insurance will come back into force once your back on the public road. They cant cancel your policy for what you decide to do in private as long as you drive it in the manner intended on the highway. I'd also argue that they cant refuse to pay out if you use the wrong brand of tyre! As long as they are the right size and load/speed rating then they are fine. Look at any 10 year old hack in the street. They usually have either modern equivalents from reputable brands or cheap far eastern tat. The original tyres for such cars are no longer made???

Back to the original question...If I were you I'd get a set of Kumho Ecsta Sports KU31s fitted to the 15s. You can get 195/50R15s for £32 ea and EVO said they were pretty good in a recent test. Just lacking in feel. You should find a back street Kumho dealer and get them to recommend what the widest tyres which you could fit on the rim. You may not be able to go too wide though. I only suggested 195/50 as they are common as muck and cheap. They will shorten your gearing a bit and lower it slightly but that wont matter on track. Geo will be fine too. Its not like you are fitting crossply slicks!! Also, check your brake pads before and after your sessions, cool the car gradually (dont key off as soon as you get back to the paddock), check your oil (keep it on the max mark, take spare you will burn a bit, and make sure there's nothing loose in the car.

Have fun and play safe!!

[J1JPE]

thanks guys, 15s are fitted with tyres which I'd use as are;

DOES ANYBODY know how the tracking, alignment on the R56 Cooper for 16" RFs will affect the handling if I put them 15s on ?

UKI (MINI Cover) point was interesting; have found the tele-sales bods make it up as they go along & say what they personally think should be the case rather than knowing or checking the company policy or insurance policy documentation

Know I'll not be covered on track but expect them to cover me on the road going & coming back; will check policy wording tho' ;}

[MINIAC]

If you're going on the track you want more rubber on the road ... certainly not 175 width tires.

[bob corbishley]

The tracking/alignment wont change a bit. If the car is set up correct then it doesn't really matter what tyres you fit.

Toe in wont change but if you were tracking it a lot you may want to play with this to increase steering feel at the expense of high speed stability (i.e. the front wheels point inwards normally to keep the car tracking straight but this can reduce feel a little I think).

Camber wont change either with the tyres but it may be possible to make adjustments to increase grip and reduce understeer but again these are for race type situations.

The only real time when you need to make significant changes to suspension settings is when you change from radial to cross ply construction, but you dont need to worry about this.

The only thing you'll notice with the std 175s on track is

A: how rediculously slow you'll be becasue it'll wash out on the corners, you'll be a mobile road block and wont win yourself any new friends
B: how the tyres will overheat and melt. - high efficiency road tyres will melt and crumle away, they just wont be any fun hence my comment about banging some Kumhos on.

I've checked the technical guides this AM. It appears that 195/50s are permitted on a 5.5J*15 rim. They'll shorten your gearing by about 6%. It is also permitted to fit a 205/50R15 which are £45ea, they'll shorten the gearing by 3.5%, but they may look a bit baloonlike.

[NeuroBeaker]

Here's a link so you can calculate tyre size alternatives. I got it from someone else on MINI2, but I can't remember who now. Anyway, here you go:

Tyre Size Calculator

From this, we can calculate the relative differences in in the speedometer estimation of your velocity and therefore the percentage change to gearing ratios as well. I've ignored any tire size above 205mm in width, as for the 5.5J rim (the 7-hole MINI 15" alloys) any tire wider than this is unacceptable to fit due to safety concerns (i.e. the tyre could roll off the rim) - according to an e-mail I have from the European Tyre and Rim Technical Organisation (or ETRTO for short) where they advised against a 215mm width.

The following wider alternatives to 175/65/15 will shorten your gearing (aid acceleration / reduce top speed), your speedometer will overestimate your speed, and your mileage on the clock will increase disproportionately to distance actually covered:

• 205/55/15: speedometer will overestimate speed: +0.33%
• 185/60/15: speedometer will overestimate speed: +0.90%
• 195/55/15: speedometer will overestimate speed: +2.14%
• 205/50/15: speedometer will overestimate speed: +3.70%
• 185/55/15: speedometer will overestimate speed: +3.94%
• 195/50/15: speedometer will overestimate speed: +5.34%

The following wider alternatives to 175/65/15 will lengthen your gearing (harm acceleration / increase top speed), your speedometer will underestimate your speed, and your mileage on the clock will be under-reported for distance actually covered:

• 195/60/15: speedometer will underestimate speed: -1.07%
• 185/65/15: speedometer will underestimate speed: -2.14%
• 205/60/15: speedometer will underestimate speed: -3.04%
• 195/65/15: speedometer will underestimate speed: -4.27%
• 205/65/15: speedometer will underestimate speed: -6.41%

Although, do bear in mind that the speedometer currently overestimates your speed to start with, but not sure what the OEM overestimate actually is though - you'll have to ask someone else for that.

As an example, let's assume that your speedometer currently overestimates your speed by 3%. If you fit a 205/55/15 tyre to your 15" alloys (my preferred option for once I change insurers), this will further increase the overestimation by the speedometer by the above listed percentage:

OEM overestimation:

60mph actual speed + 3% overestimation = 61.8mph reported

OEM overestimation + overestimation by tyre fitments:

60mph actual speed + 3% overestimation + 0.33% overestimation = 62.00394mph

Note that is is more than a 3.33% overestimation, which would have come out as:

60mph actual speed + 3.33% overestimation = 61.998mph

While that's not such a big difference for this tyre selection, a tyre which introduces a larger percentage change would induce a larger difference if not taken into account in this way.

So hopefully that's useful. Let us know how you get on.

All the best,
Andrew.

[Interludio44]

Quote: Originally Posted by ARCrawford (original)

Although, do bear in mind that the speedometer currently overestimates your speed to start with, but not sure what the OEM overestimate actually is though - you'll have to ask someone else for that.

Does anyone know what the OEM overestimate is?
Sorry to drift off-topic a bit.

[J1JPE]

thx guys, so I have 175/65-15's or 195/55 -16s (Actually Goodyear Excellence ROF not the Dunlops as I thought - sorry)

the 195s are better being wider hence better grip

BUT the 15 wheels are much lighter, lower centre of gravity, shorter gearing etc and I dont care if I wear them out as I'll put the RFs back on to go home anyway ...

so, I'm thinking to do a few laps with the 16s to get base laptimes & learn the track then switch to the 15s, check laptimes / evaluate performance again and poss go back to the 16s just before the end of the day to see if my lines, confidence etc have given any improvement in laptimes rather than just the different wheels ...

Will then be looking for a set of track tyres

for which Kumho Ecsta Sports KU31s 195/50s or a 205/55 tyre wud be ideal ...

Bob, really appreciate your points about brakes & cooling down in the pits

Am definitely also going to fit the 15s and do a road test to see how they corner, grip if wet, check ACS under acceleration etc before carrying them to the track with a jack & brace

If theyre no good, I'll just buy a secondhand set of track wheels ...

Just need to book the Circuit Days event at Oulton Park on Jan 19th, persuade my mate to pit crew, pax and borrow a helmet from his brother now

any thoughts on tyre pressures for the track PLEASE guys ?

lower than road ?
same front & back or higher at front ?
etc

[bob corbishley]

The stock speedo error is between 0 and 10% by law.

You mustn't be seen to do any lap timing or data logging at a track day. It invalidates the track day companies insurance. They will either confiscate your timing gear or just throw you out. You can analyse your data when you get home afterwards by taking logs off camcorder footage or downloading from built in loggers if you have them, but not while you're at the track.

I'd stick with stock pressures for now. You would need to measure the temps across the width of the tyre to determine how well they are performing and thats a bit full on really.

Considering you can sh@g a set of tyres in one day easily I'd buy the cheapest size there is. 195/50/15s appear good value and shorten your gearing. You'll never max out a mini at Oulton.

[J1JPE]

Quote: Originally Posted by bob corbishley (original)

The stock speedo error is between 0 and 10% by law.

You mustn't be seen to do any lap timing or data logging at a track day. It invalidates the track day companies insurance. They will either confiscate your timing gear or just throw you out. You can analyse your data when you get home afterwards by taking logs off camcorder footage or downloading from built in loggers if you have them, but not while you're at the track.

I'd stick with stock pressures for now. You would need to measure the temps across the width of the tyre to determine how well they are performing and thats a bit full on really.

Considering you can sh@g a set of tyres in one day easily I'd buy the cheapest size there is. 195/50/15s appear good value and shorten your gearing. You'll never max out a mini at Oulton.

All I was going to do was press the start, lap & stop buttons on my wristwatch ....

Used the stopwatch on my mobile from the pitwall last time to 'assess how quickly different cars came back past me' and didnt get hassled by the organisers ... maybe just lucky

Guess I'll have to tell my mate to leave the pit board at home & stop practising his lean out signals ...

thanks for you advice on pressures