replacing brake discs

[sholtby]

Thanks Andy. Your discs seem to be wearing better than mine! I think I will go for the grooved discs next time. The holes on my drilled discs are usually full of brake dust anyway.

Simon

[Cypher007]

ok. but surely if the discs are bigger you need a larger pad to cover the extra width of the braking area? or are 302's just bigger in diameter with a larger non friction area in the centre of the disc eg. a 280mm disc uses a say 50mm wide pad so the frition area is 50mm wide give or take a couple of milimeters either side of the pad, and on a 302mm its 50mm with say a couple of milimeters on the outside edge and 20mm in the centre.

[Simon J]

The pads are the same for both disc sizes. Don't forget that the area of the pad is irrelevant in terms of braking torque - it only affects fade resistance (and to some extent the rate of wear). Presumably Volvo didn't reckon that it was worth engineering larger calipers and pads to go with the bigger discs just to provide a marginal increase in fade resistance, when the alternative was a simple extension bracket for the existing caliper and pad combination. The increased braking torque due to the larger disc diameter - almost 8% - is the same in either case.

Simon J

[bobcat]

>The pads are the same for both disc sizes. Don't forget that
>the area of the pad is irrelevant in terms of braking torque -
>it only affects fade resistance (and to some extent the rate
>of wear). Presumably Volvo didn't reckon that it was worth
>engineering larger calipers and pads to go with the bigger
>discs just to provide a marginal increase in fade resistance,
>when the alternative was a simple extension bracket for the
>existing caliper and pad combination. The increased braking
>torque due to the larger disc diameter - almost 8% - is the
>same in either case.
>
>Simon J

dont think volvo did it for fade resistance, to cure that they would have just had to fit better pads and brake fluid.

im sure it was more to do with warping, if you compare the 280mm to the 302mm's they are differences in the hub design and the vents. the 302's arnt just a scaled up 280.

[Simon J]

The point I was making was that to have increased the pad size (and thus presumably caliper size as well) would only have had an impact, and a marginal one at that, on fade resistance, so it was probably not worth doing. They were presumably satisfied that by increasing the disc size, and changing its design, they could address the weakness of the 280 brakes. Which of course raises the question - why did they continue to use the 280 brakes on the C70, including the T5 - up to last year?

[bobcat]

>The point I was making was that to have increased the pad
>size (and thus presumably caliper size as well) would only
>have had an impact, and a marginal one at that, on fade
>resistance, so it was probably not worth doing. They were
>presumably satisfied that by increasing the disc size, and
>changing its design, they could address the weakness of the
>280 brakes. Which of course raises the question - why did they
>continue to use the 280 brakes on the C70, including the T5 -
>up to last year?

it wasnt about fade, thats why they left the pad size alone, it was to address the 280 warping problems.

why make bigger discs, bigger carriers and have to fit bigger wheels to address fade. fade it to do with the brake pads and fluid. if they had a problem with fade they would have just fitted better pads, but the 1144 compound pads were fine and not the problem.

to address the warping, volvo made the discs bigger and modified the design of the hub and cooling veins.

the s70 and c70 t5 did come with 302's!! but only if the owner wanted 16" wheels. if they wanted 15" wheels then they couldnt have 302's as they wouldnt fit.

for those up on there volvo's, looking at the front discs is a way to tell if a c70 is a t5.

dont the p2 70's use 305mm front discs now!!

when i ordered my 302's i ordered them from a c70 t5.

[Simon J]

We are saying the same thing, bobcat! The only benefit of increasing pad size would have been to address fade, and that was apparently not what they were trying to do. Hence they kept the calipers and pads the same size.

But you're not correct about the C70 T5s. I don't know if C70s ever came with 15" wheels, but certainly since 1999 they have only had either 16", 17" or 18" ones.

For MY2003, the T5s were specified with 302s but not actually delivered with them. That was how I ended up getting the 320s (not 302s) as I refused to accept the 280s that the car came with. After a long argument with Volvo (they claimed it was a mistake in the brochure!) they bought me off with a concessionary price for the big brakes.

For MY 2004, all variants of the C70, including T5s, were specified with 280s (perhaps as a result of my argument with them the previous year!); but for the current year they are now all specified with 302s!! So you can't be sure that just because a C70 has 280 brakes that it's not a T5.

Rgds,

Simon J

[PAZ3154]

part no.8602456 are available from your dealer for £28.00 each plus vat exchange

[NugentS]

>Best bet for these calliper carriers would probably be
>Braydon Motor Coy., Downs Road, London E5.
>
>There is a link to them at the back of my site.
>
>
>
>Don.Norchi.
>
>www.kalmar-union.com
>
>TME software for serious Volvo Tuning.

OR the club parts supplier Nordic which is where I got my 302mm discs and caliper carriers from.

Sean

[sarge]

My Dad's '98 S70 T5 has 280s.

Sarge
'99 V70 AWD