Big Brakes!!

[960kg]

It is best to try different pad materials like Ferodo DS2000 before fitting a larger disc, perhaps ok to go up one size but this has to be carefully considered due to unsprung weight on the suspension. The less unsprung weight the better the suspension reacts to do it`s job properly so doing track days this is most important as one performance gain defeats another so then where are you?

Take Brands for example i have driven around there many times especially back in the late `60`s and although the track looks a normal road from the spectators point of view when your on the track it is wide and and a never ending strip of asphalt and just swallows the bhp you have into oblivion.

The extra diameter of those large discs the rotating mass, must be accelerated/decelerated every time the speed changes, and it's harder to accelerate the rotating mass. Since most rotating mass (aside from the engine and the tranny) is unsprung weight (half-shafts, wheels, brake rotors), a reduction in unsprung weight generally entails a reduction in rotating mass, which helps acceleration. It is rotating mass that is roughly 3 times harder to accelerate than normal weight. Plain old unsprung weight is not any harder to accelerate. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly (in the direction of the vehicle's travel) and rotationally (in the direction of its spin).

As for a reduction in unsprung weight independant from rotating mass, this generally improves the suspension's ability to work properly. Unsprung weight contributes to inertia in the suspension, which in turn affects the geometry assumed by the suspension.

Racing cars are different to road cars!

[DXMachina]

Thank you 960kg for a very interesting post. I was aware that reduced unsprung weight was good (its something thats repeated often) but not why.

I note from looking at the photo of the 335mm disks that they have a ring of rivets around the hub, suggesting it is multiple parts connected together. When I changed my V40 brakes for genuine components, the disk-braking surface was contiguous with the hub part as a single huge casting

Would this be so the larger disk can use lighter materials for part of it - presumably to save weight? or just because the larger an item, the harder it is to cast as one part.

Either way I'd be interested to see a weight comparison between these new multi-part disks and the single-casting Volvo part.

[960kg]

Those large 335 discs maybe just the way they have to do it to get that size from multi manufacturers parts!

Ok , so i know V70 but still Volvo...but they did a superb bit of headbashing to improve the braking setup from 285mm discs to get the 305mm discs with the same size Caliper & Disc Pads.

Look at the pic. and you will see both sizes....i had the 285 on my motor and converted it to 305 simply by just getting the larger pad Carrier to cover the extra diameter which bolted exactly into the same holes on the hub.

Although only 20mm larger in diam. that is 10mm either side but the surface breaking area is that width 10mm but it covers all around the circumference so the extra area is quite a bit. I have never worked it out but also to aid the cooling Volvo designed the centre part of the disc differently to allow better air flow to cool the discs giving better heat dissipation. The result is quite astounding in braking performance with quite a cheap conversion using existing components calipers and pads.

Probably the unsprung weight is very similar...but gives a superb difference in braking effect.....this is what one could call Volvo Engineering!

[mitchyboy01]

The main advantage is the extra rotating mass is able to dissipate heat a lot more effectively thus reducing fade. I have made my brakes fade far too easily on all Volvos I've had. I'd rather have a little more unspung weight but have brakes that still work after 2 laps. I don't think they will give more braking power as the stock brakes can lock the wheels, it's just the ability to take repeated hard braking and not fade to nothing. Personally having driven an 850 with 302's I thought they were no better than stock.

Anyway, Ill get them fitted and report back. Who knows until I've tried them. I got such a great deal it's a win win for me anyway. Not to mention they will look awesome and are a rare sight on any Volvo. Most people go for power on a shoestring (me being one) and put up with their awful brakes.

[happy diver]

Nothing worse than brake fade, having street driven well within safety limits.

The angle of the brake hose bracket on the front struts, place undue angular stress where the hose enters the fitting, causing them to fail prematurely

[960kg]

Good luck with what you are doing Mitch....but you could spend your money on better things to reduce a timed lap rather than those humongous discs.....been there done it, but then each to his own!

If you use your brakes too much on a track then your in the wrong gear and not reading the road. Jim Clarks disc pads according to history lasted 3 times longer than any other competetive driver in the same Lotus Cortina, which means it`s the way you drive!

The 305 discs are a lot better than the 285 on the 850 as i have found out...Volvo do not waste there energies are wasteful products!!!....that is why they are fitted to later models.

[mitchyboy01]

The Hi Spec 6 pot is listed as billet aluminium and 2400g. I may have a t4 caliper in the garage so I can weigh it for a comparison.

I have read that the disc weight of the kit is lighter than most stock discs so I think any unsprung weight issue is minor and could even be better than stock.

[mitchyboy01]

Originally Posted by 960kg

Good luck with what you are doing Mitch....but you could spend your money on better things to reduce a timed lap rather than those humongous discs.....been there done it, but then each to his own!

If you use your brakes too much on a track then your in the wrong gear and not reading the road. Jim Clarks disc pads according to history lasted 3 times longer than any other competetive driver in the same Lotus Cortina, which means it`s the way you drive!

The 305 discs are a lot better than the 285 on the 850 as i have found out...Volvo do not waste there energies are wasteful products!!!....that is why they are fitted to later models.

Don't start saying that better brakes aren't important on track as this is just nonsense. If I was going for more bhp you would say money would be better spent on brakes. It's just the way you are.

[960kg]

Originally Posted by mitchyboy01

Don't start saying that better brakes aren't important on track as this is just nonsense. If I was going for more bhp you would say money would be better spent on brakes. It's just the way you are.

Mitch , i really think you have a problem?

I did not say "brakes are not important on a track" you just did!......

You are going over the top with your brakes as you have no idea at all and i try to help you what to look for but you continually write abuse to me and cannot even consider my opinion.

So what prat you are to ignore advice when as i said years ago i have been there and done it. I know things you can do to make a lot of track day owners stand back and wonder why your quicker......but you just like chav brakes which is utterly rediculous on such a small motor with only 237bhp.

My motor at the moment has not quite 30% more than your power in a heavier car and my brakes are superb so i must drive smoother than you and mine don`t fade... i use to Marshall at Brands Hatch in the late `60`s and `70`s and also went to there drive school so you can`t teach me very much about driving ability and brakes.......so shall we end it here?

[mitchyboy01]

Originally Posted by 960kg

Mitch , i really think you have a problem?

I did not say "brakes are not important on a track" you just did!......

You are going over the top with your brakes as you have no idea at all and i try to help you what to look for but you continually write abuse to me and cannot even consider my opinion.

So what prat you are to ignore advice when as i said years ago i have been there and done it. I know things you can do to make a lot of track day owners stand back and wonder why your quicker......but you just like chav brakes which is utterly rediculous on such a small motor with only 237bhp.

My motor at the moment has not quite 30% more than your power in a heavier car and my brakes are superb so i must drive smoother than you and mine don`t fade... i use to Marshall at Brands Hatch in the late `60`s and `70`s and also went to there drive school so you can`t teach me very much about driving ability and brakes.......so shall we end it here?

30% more power and 30% extra weight = similar performance apart from usually the lighter car will brake and handle better.

I'll tell you about unsprung weight though. T4 calipers minus pads are nearly 2kg heavier than the HiSpec ones. Not to mention the extra surface area of the larger kit for heat dissipation. Now stop trolling me please.

Times have moved on since horse and cart so stop ruining my threads. If I put up an F1 car you would say it was awful because it is mine. Only you could fault someone improving the braking (and unsprung weight) of their car.

I am putting better brakes on my car for doing some track time. Now answer me honestly. is this a bad thing?

Polybush is in the pipeline when funds allow and I have various sets of coilovers springs I have bought to experiment with handing. What else do you recommend?