Internal diameter of the TVR 15" rim in mm anyone?
Discussion
285mm fits easily into the standard 15" rims. Tower View managed to squeeze 300mm brakes into the same rims using Wilwood superlite 4 pot calipers, but it was a very tight squeeze; others have tried and failed. 300mm fits easily into 16" rims.
In any case, I would advise against going over 285mm on the front unless you address the brake balance. 285 should be more than enough for most people.
In any case, I would advise against going over 285mm on the front unless you address the brake balance. 285 should be more than enough for most people.
Rally Designs have two 300mm options listed in their catalogue, a 4pot and a 6pot!!!, both designed to fit in the std 15inch rims, prices are on application so expect to pay around 1K, possibly better to go for 285mm 4 pot kit at around 500GBP, and do the rears at the same time to achieve a better balance. IMHO
If you do go the 6pot route I'd very interested to know how it turns out.
If you do go the 6pot route I'd very interested to know how it turns out.
I know (experienced) others have expressed concern over balance but the front/rear balance seems spot on to me (standard size drilled and grooved discs, braided hoses, Ferodo pads, racing fluid - Griff 500 on SO3s). Doing some braking tests in the dry I have never been able to get the rears to lock up even downhill when there is very little weight on them. Upgrading only the fronts will surely mess this balance up? I wonder if anyone has done a series of braking tests, uphill/level/downhill and wet/dry to see whether the upgraded fronts really do improve braking distances? My guess is that downhill in the dry they will show an improvement but everywhere else they may actually be worse! 
If the static balance is wrong, the best way to show it up is to drive the car round a corner fairly close to the point of sliding in slippery conditions, and then brake gently. The closer you are to sliding the less pressure it will take on the brakes to show the effect. If you have too much front bias the car will start to understeer when you brake. If you have too much rear bias the car will start to oversteer. Be carefull though because under these conditions it will not take much braking to lock a wheel and if the rear locks the car will try to spin, so you need to pick somewhere with plenty of space and nobody else around.
It does seem common for TVRs to have too much (IMO) rear braking, but it sounds as if the balance may be about right in your case, which is good news.
It does seem common for TVRs to have too much (IMO) rear braking, but it sounds as if the balance may be about right in your case, which is good news.
That's a very tricky test though! 
I've tried that but found that the biggest influence was how hard I pressed the pedal - slightly too much and the fronts slide, too little and the rears slide (unless you reduce lock at the same time - not opposite lock - just a small amount). It would be easy to misinterpret the results I would think. Definitely need lots of room!!
I've tried that but found that the biggest influence was how hard I pressed the pedal - slightly too much and the fronts slide, too little and the rears slide (unless you reduce lock at the same time - not opposite lock - just a small amount). It would be easy to misinterpret the results I would think. Definitely need lots of room!!The 300mm kits do not fit the TVR wheels. Or to be more accurate it is a lottery as there is a lot of variation on the upright/calliper/wheel position and all it takes is a mm or two variation and the calliper etc fouls the wheel or upright. There is also the potential problem of slightly distorting the wheel by curbing or big pothole and then finding the calliper is grinding through the wheel. The clearance is extremely tight.
My Griff 500 has a 285mm upgrade with Wilwood 4 pot callipers, drilled and grooved discs front and rear with DS2000 pads. It was the test bed for Tower Views upgrade and was based on the 520's brake spec from a few seasons ago. Went for 285 because of cost and fitting issues.
The performance is simply superb. Yes braking is a big improvement and the setup works from cold. Been unable to induce fade on track days. The balance is very good with an excellent progressive feel. The rears do not need upgrading at all and in most cases it is a waste of money as the majority of the car's braking is provided by the front anyway due to the weight transfer.
Steve
www.tvrbooks.co.uk
Leadfoot said:
Go for the 285mm version instead as it will fit the 15" rim.
I had this for a couple of years on my Griff, then changed to 300mm discs - there was only a marginal increase in braking power, not enough to justify the extra cost/changing to bigger wheels.
I had the 285 kit too. As Steve Heath says - great stopping power. Don't worry about them looking puny - they fill the wheel 'gap' nicely:
shpub said:
... The rears do not need upgrading at all and in most cases it is a waste of money as the majority of the car's braking is provided by the front anyway due to the weight transfer.
Steve
www.tvrbooks.co.uk
I accept the fronts do most of the braking BUT to get the best performance you also want the rears doing as much as they can.
In the right conditions, ie hot, dry, grippy surface, then yes you get more weight transfer which gives the fronts more traction for more braking which gives more weight transfer and so on and so on until either the brakes can do no more or the tyres slip. I have to say that my brakes will not lock at all in these conditions going downhill - hence why I can see the upgrade would make a difference here.
In all other circumstances though the standard brakes will easily lock the fronts so by upgrading the front brakes (bringing the bias forwards) you will end up locking them earlier and the rears will be doing less. Your overall stopping distance will increase, I would have thought.
I can see other benefits with larger brakes like better heat dissipation and better feel which may be justification enough. Don't mean to hi-jack the thread but this seemed relevant.
GarryM said:
In all other circumstances though the standard brakes will easily lock the fronts so by upgrading the front brakes (bringing the bias forwards) you will end up locking them earlier and the rears will be doing less. Your overall stopping distance will increase, I would have thought.
Absolutely right. When the existing brake bias is too far back, upgrading the front brakes improves the overall brake balance as well as reducing the tendancy to overheat the front brakes. But you can have too much of a good thing, and if your front upgrade leaves the bias too far forwards then your overall stopping distance can increase.
shpub said:
Which car? Which standard wheel? Doesn't really matter as that kit won't fit a 15 inch anyway
Steve,
Have 300mm 4pot billet (dear I say) Hi-spec in 15" standard 350i wheels. So it can be done.
Ok, the weights have to be positioned cleverly but that is all.
Agree that it depends on the rim design, and perhaps I was lucky.
Rob
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