Wheels, tyres an dogbox q's

[nky_84]

Hi guys,

Looking to do a few upgrades over the winter to my bmw k head sprinter (153bhp).

Gearbox - has straight cut drops, plate LSD matching shafts and CWP but basically standard internals that i'm surprised have lasted so long tbh. Before this blows up and takes my engine with it, ivebeenlooking at MED's dogbox kit www.med-engineering.co.uk/catalogue/gearbox-transm... Anyone have any experience of this kit or would suggest an alternative?

Wheels - currently running 12x6 minilites with way past best a048s. Would like to take the step up to slicks next season and it seems that the general consensus is 13x7 but i have no idea when it comes to offset and whether split rims are worth the extra cash. Currently looking at minispeed.co.uk/content/minispeed-black-7x13-wheels-set-four for the cheaper option or i do like the look of some of force racingsrims-www.force-racing.co.uk/wheels-13/....

Tyres - Seems that Avon want the best part of £700 for a set of 4 Budget option is to get some harder formula ford/ renualt jobs for <£100 even if they are just for testing of getting used to slicks.

Any advice or suggestionson any of theabove would be great!

[FWDRacer]

Dogbox - Do you drive this beastie on the road? If so a dogbox isn't out of the question, but you'll need to heel-&-toe or double de-clutch (ask your dad) as a bare minimum or you'll be crunching the box as you've not speed matched the box on downshift. Upshift isn't an issue - you might not even need the clutch - light lift and through into the next cog. Dogbox and it's inherent strength/lack of bits to break (baulk rings) will be one last thing that you don't need to worry about, especially if you are worried about the torque output - the box will outlive the engine I'd reckon.

Wheels/tyres. Much better range of tyres in 10" if you track it (bespoke racing rubber - Hosier slicks/Miglia Dunlops on 6.5/7x10" - 13" inch wheel will screw the handling. Mini's handle best on 10" wheels.

[DanGT]

12" are not to bad but 10" (now days) are the one to go for if you can get them round your brakes.

[nky_84]

Car is used for sprinting only, and is not road legal. I'm well aware of H&T and double de-clutch, however doing it well and quickly whilst picking the very last breaking point is a another story... Sounds good about the rest of it, yes i've heard about almost flat upshifts :-)


Is there really a better range of tyres for 10" than 13" or are we talking mini specific here? Trouble is, i have some nice shiny KAD 4pots that will not fit under 10's. I've read that the 10" vs 13" debate and it seems like there is a pretty even split if the regs allow - 2 votes for 10's noted though!

[Skyedriver]

How long is a sprint course nowerdays?
Would FF tyres get up to heat before you crossed the finish line?
Doubt they would in a hillclimb but I suppose you might get a reasonable s/h set of hillclimb/sprint compound at theend of this season.

[rww]

nky_84 said:

Car is used for sprinting only, and is not road legal. I'm well aware of H&T and double de-clutch, however doing it well and quickly whilst picking the very last breaking point is a another story... Sounds good about the rest of it, yes i've heard about almost flat upshifts :-)


Is there really a better range of tyres for 10" than 13" or are we talking mini specific here? Trouble is, i have some nice shiny KAD 4pots that will not fit under 10's. I've read that the 10" vs 13" debate and it seems like there is a pretty even split if the regs allow - 2 votes for 10's noted though!

We sprinted using Miglia (10") rear slicks on the front and rear as the rear compounds are the softest Dunlop available. Hoosier also make a wide/soft 10" tyre but we have not used them. Tyre temperature in sprinting is critical - the second driver of our Mini could have 1 sec. or more advantage over the first simply through running on warmed tyres.
We also used a Swiftune (Quaife) dog box.No heeling and toeing required on track but we never flat shifted.It has proved extremely reliable over 5 years of sprinting and racing. Similarly the Timken roller conversion(not plain) s/c drop gears which you will certainly require if you are putting 150+bhp through the drive train. Then there are the driveshafts - standard ones break like carrots both from standing starts and on braking downchanges.
Bill Richards Mini Clubman uses 13" Avons very successfully on the SE circuits but he has developed that car over many seasons. By using 10" wheels there is a known geometry set up which works out of the box.

[chris_w]

rww said:

We sprinted using Miglia (10") rear slicks on the front and rear as the rear compounds are the softest Dunlop available.

They were uncut wets as well weren't they?

[nky_84]

Skyedriver said:

How long is a sprint course nowerdays?
Would FF tyres get up to heat before you crossed the finish line?
Doubt they would in a hillclimb but I suppose you might get a reasonable s/h set of hillclimb/sprint compound at theend of this season.

approx 90seconds per run. I've been told that 1st lap, they are about the same, maybe a little worse that ao48s but after there is heat in them, they offer much more grip. Appropriate avons will give far more grip, its jus the FF's can be had for £80 a set whereas avons are looking like £800 and it is just a hobby after all...

I change my mind on an almost hourly basis, but for the sake of £80, they might just be worth a go, especially if its just for preseason.

[Jon Brown]

For the sake of £80 I would give it ago but i have no experience of hilclimbs etc.

Can you post up some details of your engine spec, as i was looking at a similar conversion on my 998.

[lee76]

rww said:

Bill Richards Mini Clubman uses 13" Avons very successfully on the SE circuits but he has developed that car over many seasons. By using 10" wheels there is a known geometry set up which works out of the box.

The only reason we converted from 10" to 13" was due to the 10" tyres giving up the ghost after 7 or so laps due to the power/torque of the engine. The 13" hang on to the end of a race and give more grip but the handling of the car is not as good as 10".I also made alot of changes to the car to make the 13" work as the Avons have a stiff kevlar sidewall construction and are designed to work on a car with downforce not a lightweight mini. If it were my choice (from previous experience and years of running cars) i would always run 10" on a hillclimb/sprint car and used rear Miglia tyres are common enough to come by.

[nky_84]

Where would one enquire about Miglia slicks? New or part worn. In terms of wheel options for 10's, it seems there is little or nothing available in 10x7 outwith expensive / split rims?

Do you have more info on the timken roller conversion as i only have s/c drops just now. Care to point me in the right direction of the known geo setup for 10" wheels too? :-)

[lee76]

A mig slick will run on a 6x10 fine. Try - gerald dale motorsport, mini 7 racing club, Endaf Owens (sheepspeed.com) or Peter vickers (altered image coachworks)

[FWDRacer]

Or Dunlop Motorsports at Fort Dunlop in Brum...

Contact 0121 3844444 switchboard / 0121306 7031/7059 direct.

[chris_w]

nky_84 said:

In terms of wheel options for 10's, it seems there is little or nothing available in 10x7 outwith expensive / split rims?

We use mini specials with a Force racing split rim conversion:

http://www.force-racing.co.uk/wheels-10/

[Runty]

I used to hillclimb/sprint a Mini with a Swiftune dog box and 7.5 Hoosier r25 soft slicks on 10" rims.....You can check out youtube for in car footage. Search for Bantoracer. No problems with slicks or box.....but I did have a Quaiffe ATB fitted. Good Luck.