Turbo k100 Braking questions.
Turbo Mini Forums

hey everyone, i was just wondering if anybody could lend thier knowledge to this problem.

i am soon to be building a turbo k but i want to get as much planing sorted as possible first. so im onto planing for the braking setup. i want 10" wheels but im not sure that 7.5/7.9" 4-pots would be enough to handle the circa 200bhp/180f/lb that i will be aiming for. would it be best to go for the seductive tarox/kad 6's instead which would mean the need for 13" wheels and a reduction in handling.

also on the subject would i need/be better of going for 13's to keep wheelspin down or am i just over thinking the whole thing and 4pots will be enough stopping power and 10's wont wheelspin as much (with decent launch ability) as im thinking?

just trying to sort my plans out and get as much info on what im about to do rather than go the long way around and spend more money than i need to when someone already knows and could help me.

cheers for any help you may have. James.

Hi,
Personally I'd always go for 13's, more rubber on the ground, more room for bigger brakes.
A good 4pot vented setup with grooved discs and good pads should pull you up in a hurry
Cheers,
Gavin :)

Edited by Bat on 17th Aug, 2007.

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Im the opposite...lol....I'd go for 10's with some ally 4 pots, altough saying that im doing a similar thing but sticking with standard S setup?

10's look better IMO.

Not much help I know with 2 people saying the complete opposite, but there is more than one way to skin a cat!

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1/4mile in 13.2sec @ 111 terminal on 15psi

I like the idea bout 10's (handling acceleration) but alot of people have changed to 13s due to "being overwhelmed"

If you go 10s id just get a set of ally four pots as matty said.

But 13s too many options. Cheapest would be metro turbo, which i reckon would work just as well.

Back once again like a renegade master

In theory 13s should be better as the lower profile means less tyre roll and therefore the contact patch remains where you want it, that said I run 10s.

Brakes always seems to be a bit of a can of worms lol, so many opinions!

Quite a lot of people with very powerful minis only run the S setup (with uprated pads) and reckon its fine, Galiofly for example is running 200+bhp with S brakes and has posted they are fine for trackdays and the like, and judging my his metro racing results he works them pretty hard! LOL

However, I have S brakes with sub 100 brake and often get fade on the road, dispite not driving that hard....

Why?

I think its down to the fact that on the road you do an awful lot more actual stopping rather than slowing down. when you stop quickly you cane the arse out of the pads, then leave them sitting there with no airflow to dissipate the heat. this can't be helped by the small surface area of the S disc's, plus the small area of the pads.

I think the size of the pads in the fiesta conversion along with the extra disc size really helps it in this instance. I'd guess that the disc must have maybe 20% extra surface area, and the pads must be getting on for twice the size of S ones so will be able to dissipate a coniderable amount of heat out of the disc into the caliper/hub. (which could be a bad thing from a wheelbearing/brake fluid view)

A step further would of course be vented disc's.

I've never had a problem with my brakes, under 10" wheels using the minispares alloy calipers. Std master cylinder, nothing trick, stops very very well!

Team Racing

cheers people! thats helped loads. i really wanted to go for 10's due to the better handling, but i just wasnt sure whether ally 4-pots would be enough, apparently i was wrong .

the comment about the low profile tyres is sort of wrong. i dont want to seem like im stomping on anyones views and trying to be a "im right your wrong" type of person and if it sounds like that then im sorry. but it infact it is the extra movement in the sidewall that makes the handling better on the tens. because this means that you can stiffen the car right up so that it is tight into the corners but with the reflex in the sidewalls when you hit a bump going into the corners you don't "bounce up" excessively taking traction away from your the front wheels causing the car to handle cack. the sidewalls absorb the smaller bumps and, to a point, counteract the the stiffness in the car whilst still allowing you to be tight into the corners.

look at the miglia's that run on 10's and high profiles and then also F1 cars. its a track proven set-up.
rant over. sorry :( haha

bit of a cheeky newbie rant. pushing my luck ey.

I have gone through this a few times on the site and there is quite a compleling argument for 13s detailed by myself if you wish to search for it.

To cut a long story short basically a Mini set-up correctly for 13x6" wheels (ET20 offset +/-2) will be quicker around the same circuit (plus the advantage of bigger brakes on top!!) than a car on 10" wheels.

The reason why a lot of people prefer the handling on 10"s is that the car feels safer and more morfigiving. The reason for this is the wheels moving around inside the tyre and softening the response of the car to your inputs, basically flattering the driver by giving him more warning that it's going to bite him but conversely is less capable of rapid direction changes and also softens any corrective inputs too.

I can't remember who it was now but a well learned gent from F1 once said that a safe car is never going to be quick ...... how very true.

The reason people like Aryton Senna were so much quicker than other around some cicuits was because he had the ability to drive a car "beyond the edge" ..... which will always be the quickest!!!!


Anyway, a Mini looks better on 13s IMHO!!!


Edited from here ......


I posted my reply as you posted that 10s handle better .........

Absolute, total, utter tosh!!!!!! Unless the laws of pyshics have changed since I was last at Univeristy (or indeed the last time I set a car up on track) that is.

1) The "bounce" as you put it in the tyres is uncontrolled and also the taller the sidewalls the less effect small changes in tyre pressure has and also it puts "dead zones" in the damping control (especialy at the infelection points of the oscillations) so it makes the car harder to fine tune.

2) Roll stiffness can only be controlled through the chassis as there are fixed points at the mountings, floppy tyres limit the effectiveness of roll bars etc. by providing uneven / uncontrolled pitch and track changes.

3) If your right everybody on hard suspension bushes is wrong ... those with rose joints are stupid ..... not sure you could make that stick. What is the point of setting geometry to a fraction of a degree and track widths to less than a mm only to allow the contact patch do whatever it likes??????

4) Migs and F1 are on the tyre sizes they are for a reason .... regulations. Look at touring cars .... see what they CHOOSE to run!

5) What you are describing is only true if you run out of travel, have the bump stops set too short into the travel or you have the springing / damping set WAY too stiff. Compliance is the key to good hangling.

A car leans on it's dampers as it changes direction .... most Minis seem to be set up massively over damped which makes them less able to follow the normal undulations. Damping (either bump or rebound) falls into two main catagories ... PACK (it's ability to react quickly) and RESISTANCE (ability to control the spring over longer travel).
High PACK damping (can think of it as smaller flow area through / round the damper piston) reduces the ability of a damper to react quickly to sharp impacts (high piston speeds) such as hitting the edge of a pot hole. Quite often cars running on rough tracks will run reduced pack to allow the car to run through it's travel and maintain controlled contact patches.
Stiffening up the pack improves the responsivness of the car to direction changes.

Resistance damping is matched to the spring and is there basically to control the springs movement. Most people find they prefer the car to be slightly overdamped (more than critical damping which means a deflection results in one full cycle, no more no less)

By balancing the damping media and other parameters it is possible to have high pack with low resistance and vice versa.

A cars springs dictate the balance of the car, both in pitch and roll, by controlling not just wheel movement individually but roll stiffness.

Often people think of the springs as the only springing medium but when there are anti-roll bars fitted they become part of the springing of the car too, but only in roll when they act as torsion bar springs (in reallity a wire spring is still a torsion bar, just arranged differently).
The key to good handling comes from balancing the vertical springing (dealing with the suspension travel) and roll control.


There is a whole list of other suspension parameters which I am not going to cover now but for all of them give rise to different compromises but one thing remains true ........

The last thing in the world you want is anything uncontrolled just flopping about in the breeze ...... like, for example .... high sidewalls!!



I really don't want to appear to be rude, those who know me well will tell you that is the exact opposite from my normal character however I do find it very difficult to read things like youre second post which are so wide of the mark as there are many people who might not have the knowledge to differentiate from fact.

My rant over :)

Edited by RogerM on 18th Aug, 2007.

Every day is a school day ...........

How fast and how expensive ...... the same question...

I think that if you are running on a nice smooth race track that a 13 may give you better grip on corners and braking, provided you can achieve the same unsprung weight as the 10 inch.

13s and stiff sidewalls will not give good braking on a bumpy road. You will just skim over the top of the bumps, particularly so if you have a heavy wheel.

The unsprung weight is the key factor, not the wheel diameter. You can get the same tyre circumference and width with either 10s or 13s. So the difference is the sidewall stiffness which is going to be higher with a 13 inch wheel. And sidewall stiffness is only any good on a smooth road.

Ultimately, the performance is down to many factors and how you use the car.

I like the look of 10s and just use my car on the road, usually bumpy ones, so I'm going with 10s and get the unsprung weight as low as possible.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

rogerm................................................................. THANKS.

my second post was based on "knowledge" that i had gain from other people via forums, books etc. obviously not as accurate as i thought.

Thanks for that its put me in my place.

i'm not a stubborn (Sp.) person and any new info is something i will take in and learn. i in no way claim to be an expert in any of these matters and so when someone like yourself tells me something like that it is somethings for me to take note of and learn. the more i know the better i will be.

Thanks again, oh and everybody ignore my second post, is now null and void.

James.

Mini_Majic ..... sorry if I came across a bit harsh. Please accept my welcome to the best, certainly the most technically credable, Mini based forum on the net........

I am more than happy to discuss anything Mini related with people, as are a lot of knowledgable people on this forum.

If your interested in handling and suspension settings then have a read of a couple of books such as;

http://www.amazon.co.uk/Chassis-Engineerin...87448988&sr=8-6

or

http://www.amazon.co.uk/Car-Suspension-Han...87448988&sr=8-5

I personally believe that, aside from the "pub BHPs", suspension is one of the most mis-represented parts of car modification ..... certainly on internet forums.



If you want to run 10" wheels then by all means do so ..... some people run what they like on the road (which in fairness if your testing a well set up Mini you should be looked up!!!) and have a special set of wheels for track use when everything becomes a bit more stress and near the limit.

I have a project in the pipeline that can only really sit on 10" wheels for shows ... nothing else would look right .... however it will never be driven on them .... to the show on 13"s (maybe 12s) and change there ...... think of how long the tyres will last on the 10s... lol.


May I respectfully suggest that you think twice before posting any "technical information" onto this forum which you can not substantiate as there are some very knowledgable and specialist people on here who might feel they have to disagree

If you are unsure, word as a question rather than a statement and you will get a much more positive response!!!!

Just a quick heads up ......

Turbo Dave ...... professional transmission engineer
JohnK .............. originator of the "off the shelf K head conversion" ... knows a bit about engines!!!!
Turbo Hogster ... what he doesn't know about Mini gearboxes isn't worth knowing

I can't be bothered (sorry) to type more but those guys are just the tip of the iceberg ...... if you want to learn about Minis TM is the place!!!!!!!

P.S. removed naughty word from my edited post ...

Edited by RogerM on 18th Aug, 2007.

Every day is a school day ...........

How fast and how expensive ...... the same question...

As Axle says unsprung weight is of untmost importance to good handling.

A lot of the 13" wheels out there are radiculously heavy ..... especially the cheap ones some of the less reputable suppliers.

Image wheels make some very nice stuff which is quite light (at a price) .... Compromotive do some very light 13s that will fit a Mini at about half the price Image would want for a set of theirs.

Every day is a school day ...........

How fast and how expensive ...... the same question...

Interesting reading roger, ive allways been undecided on 10's and 13's . Got mine on 10's at mo but could quite easyly swap to 13's . I was planning on using kad 6 pots then could swap up to a bigger disc if required.

vented 8.4" turbo discs
KAD 6 pots
MB racing 10" split rims

i cant state this as a working set up as yet as i cant tell if the clearance is enough until i get it on the car, but i think its gonna work!

Edited by andywaller on 19th Aug, 2007.

chuffing hell ... never seen that done .... good work fella!!!

That is the first proof of an 8.4" set-up UNDER 10" wheels I've personally seen!!

Edited by RogerM on 19th Aug, 2007.

Every day is a school day ...........

How fast and how expensive ...... the same question...

Thats a nice set-up. would be great to know if it works as you say.

i am really deliberating now as to what size. im more swaying towards the 13's now as per RogerM's info and going for the Tarox 6's under some nice compomotives.

one thing is for sure though! i have just ordered my Specialist Components build Diary and hopefully buying my head in the next few hours!!

Double Post!

Edited by James_H on 19th Aug, 2007.

Blooming heck Andy, that's impressive, just keep a close eye on the tyre fitters when you get the wheels balanced as there won't be much clearance for the the weights.

Well Spectrums then - same as MBs

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

woohooo!! that build diary is going to come in handy, i have just brought my k100 head for a tidy £90!!

£90 what a bargain!

rob h your right i think the balancing weights as the are at the moment will be a bit close.

doesnt carl do some force rims that allow you to use standard 8.4" brakes under 10"s?

I think the force rims to do that have quite a big offset to them, I guess the idea is to stuff them on a sportspack mini rather than a racer...

I think most of the people that use the 6 pots with 10's turn the disks down to 8.3" and move tha calipers in slightly to leave room for the stick on weights,

Thats what i've done anyway...


Oh, nice sig.... lol

for some reason I have a long history of looking like people, so far I've been called, Ade Edmonson, Cristopher Walken, Sigourney Weaver (WTF!) and Rik Mayall.

Edited by Joe C on 20th Aug, 2007.

yeah i think i may be going the 8.3" route like you were saying joe.

would be nice to run them "normal size" saves messing about on the lathe! still got to groove them though!