Outbraked by a Ford Focus...
Discussion
Targarama said:
So you had a pair that broke? Tell us more then, what happened to them?
I haven't touched them personally, but seen a few Lotus owners that have had problems with them, breaking after a track day.Try googling C44 brake pad failure, there's a few vids of them on youtube...
Personally I've always had Pagid RS14s
gruffalo said:
can not believe that OP has not changed the pads to same all round and not cheap EBC either, had far to many instances of brakes fading to nothing with those pads to ever return.
Working on it slowly... EBC Greenstuff have been removed from the rear to be replaced with Ferodo DS25HP. These are very similar to DS2500, AP Racing supply TVR Power with these for the rear and DS2500 for the front and I have had a few chats with AP about the brake compounds, coefficients of friection etc.
Front pads are, I believe, Ferodo DS2500 of unknown age / use and will be changed to fresh DS2500 next week.
In addition, to help even out the brake balance I intend to remove the Toyo T1-Sports from the front axle (had 4 new T1-Sports fitted in April) and replace them with 'Sunew Sport', keeping Toyos on the rear. The Sunew tyres are only £50 a corner, not the £160 I paid for the Toyos and this should help ensure the front brakes lock first, and also make the car understeer severely at the limit, which is of course a great handling characteristic.
Sunew tyre link here
Please don't believe that last bit about the tyre swap...
Sevenman said:
LOL... out of all those brands on that link, there isn't one I ever heard about...PascalBuyens said:
LOL... out of all those brands on that link, there isn't one I ever heard about...
I suspect they market those tyres to people who want some cheap low-profile tyres on cheap 18" wheels on cheap low-performance cars.If I had a spare set of wheels and wanted to learn to drift the car at relatively low speeds then I could see a place for those tyres.
Having been to an interesting meeting at Continental's UK tyre distribution centre last week and found out a bit more about the technology and quality control that goes into the tyres made by a premium company, and the performance in tests of some of the cheap Chinese tyres, I wouldn't touch them for road use.
Hang on a sec...
Your car is locking the rears first, so you're going to fit "less grippy" (TBC) tyres to the front?While that may stop the rear from locking first, it will only work by reducing how hard you can brake and grip is the ULTIMATE limiting factor! It's like having trouble with wheelspin reducing your acceleration, and "fixing" it by fitting a smaller engine.
In any kind of testing you need keep as many things equal as possible to eliminate them, so start with all one type/age of tyre, and all one pad compound/age (confirmed). You may also find someone got oil or grease into the front pads for instance even if they are also DS2500.
Did you check the F/R connections are correct on the m-cyl as Walford suggested (assuming it's a staggered-bore design)? If they are wrong, the low-pressure that's supposed to be going to the rear will be at the front, and vise versa.
Other suspects (general, not TVR specific) would be damaged/kinked front line/s including the solid chassis ones, front-only ABS (unlikely!), incorrect front caliper piston size (many calipers of a single design will have a few piston sizes depending on the model they fit - like BMW E30 rear saloon calipers vs touring ones....which are now randomly fitted mix-and-match style as people think they are all the same).
In terms of fitting an extra rear bias valve, even if you got it working it's a bit like fitting an upgrade to fix a problem....the problem is still there and could suddenly get worse if left.
Sorry for the long post, hope it's some help! :-)
Your car is locking the rears first, so you're going to fit "less grippy" (TBC) tyres to the front?While that may stop the rear from locking first, it will only work by reducing how hard you can brake and grip is the ULTIMATE limiting factor! It's like having trouble with wheelspin reducing your acceleration, and "fixing" it by fitting a smaller engine.
In any kind of testing you need keep as many things equal as possible to eliminate them, so start with all one type/age of tyre, and all one pad compound/age (confirmed). You may also find someone got oil or grease into the front pads for instance even if they are also DS2500.
Did you check the F/R connections are correct on the m-cyl as Walford suggested (assuming it's a staggered-bore design)? If they are wrong, the low-pressure that's supposed to be going to the rear will be at the front, and vise versa.
Other suspects (general, not TVR specific) would be damaged/kinked front line/s including the solid chassis ones, front-only ABS (unlikely!), incorrect front caliper piston size (many calipers of a single design will have a few piston sizes depending on the model they fit - like BMW E30 rear saloon calipers vs touring ones....which are now randomly fitted mix-and-match style as people think they are all the same).
In terms of fitting an extra rear bias valve, even if you got it working it's a bit like fitting an upgrade to fix a problem....the problem is still there and could suddenly get worse if left.
Sorry for the long post, hope it's some help! :-)
Keri said:
Hang on a sec...
Your car is locking the rears first, so you're going to fit "less grippy" (TBC) tyres to the front?While that may stop the rear from locking first, it will only work by reducing how hard you can brake and grip is the ULTIMATE limiting factor! It's like having trouble with wheelspin reducing your acceleration, and "fixing" it by fitting a smaller engine.
I refer to the very bottom of the post to which you refer.Your car is locking the rears first, so you're going to fit "less grippy" (TBC) tyres to the front?While that may stop the rear from locking first, it will only work by reducing how hard you can brake and grip is the ULTIMATE limiting factor! It's like having trouble with wheelspin reducing your acceleration, and "fixing" it by fitting a smaller engine.
Sevenman said:
Please don't believe that last bit about the tyre swap...
But now that you mention it, I do sometimes get wheelspin.Maybe the TVR would be better off with a nice lightweight Rover K-series engine up-front
Keri said:
In any kind of testing you need keep as many things equal as possible to eliminate them, so start with all one type/age of tyre, and all one pad compound/age (confirmed). You may also find someone got oil or grease into the front pads for instance even if they are also DS2500.
Tyres done in April, brake pads soon to be done. Also getting some further insprections done on the car.The rear bias valve is a replacement, not an addition, but it does complicate matters by giving me an extra degree of freedom so may get changed back.
Next week should see some good progress with a day set aside and 2 places to visit with the car that should be able to help.
Sevenman said:
gruffalo said:
can not believe that OP has not changed the pads to same all round and not cheap EBC either, had far to many instances of brakes fading to nothing with those pads to ever return.
Working on it slowly... EBC Greenstuff have been removed from the rear to be replaced with Ferodo DS25HP. These are very similar to DS2500, AP Racing supply TVR Power with these for the rear and DS2500 for the front and I have had a few chats with AP about the brake compounds, coefficients of friection etc.
Front pads are, I believe, Ferodo DS2500 of unknown age / use and will be changed to fresh DS2500 next week.
In addition, to help even out the brake balance I intend to remove the Toyo T1-Sports from the front axle (had 4 new T1-Sports fitted in April) and replace them with 'Sunew Sport', keeping Toyos on the rear. The Sunew tyres are only £50 a corner, not the £160 I paid for the Toyos and this should help ensure the front brakes lock first, and also make the car understeer severely at the limit, which is of course a great handling characteristic.
Sunew tyre link here
Please don't believe that last bit about the tyre swap...
Keri said:
What about the master cylinder connections - that one thing (while unlikely) if wrong will cause all the symptoms you've described?
That area has been looked at in detail by a TVR Specialist, but I can get TVR Power to double-check when it is in next week.I don't think that design of master cylinder has outputs at 2 different pressures, hence why the cars came with a brake proportioning valve in the rear line.
PascalBuyens said:
I haven't touched them personally, but seen a few Lotus owners that have had problems with them, breaking after a track day.
Try googling C44 brake pad failure, there's a few vids of them on youtube...
Personally I've always had Pagid RS14s
C44 is a full race (very old compound motorcycle pad), nothing to do with car.Try googling C44 brake pad failure, there's a few vids of them on youtube...
Personally I've always had Pagid RS14s
Winter driving is something that kills all heavily sintered brake pads, water ingresses into the compound and freezes. Compounded with all the road salt and whatever.
Hence ALL decent track suitable pads have not for road use on them.
Update - Front pads will be changed for fresh DS2500 next week.
Does anybody know the piston size in the front / rear calipers as used in the Tamora (and I assume T350 / Sagaris)?
The rears and single-piston, the fronts four-pot.
I am trying to work out what bias the valve needs to apply given different calipers and disk sizes.
Disk size front/rear is 304mm/282m and a simple calculation gives a ratio of 1.078 (there will be a more accurate way of calculating given the pad dimensions, but that would be tricky).
This means that, on disk size alone, the rear has 0.927 of the braking force of the frot.
If I know piston diameter (and hence piston area) then I can add that into the calculation and see what the bias is before a valve is fitted.
Does anybody know the piston size in the front / rear calipers as used in the Tamora (and I assume T350 / Sagaris)?
The rears and single-piston, the fronts four-pot.
I am trying to work out what bias the valve needs to apply given different calipers and disk sizes.
Disk size front/rear is 304mm/282m and a simple calculation gives a ratio of 1.078 (there will be a more accurate way of calculating given the pad dimensions, but that would be tricky).
This means that, on disk size alone, the rear has 0.927 of the braking force of the frot.
If I know piston diameter (and hence piston area) then I can add that into the calculation and see what the bias is before a valve is fitted.
Tech spec of the AP CP6600
http://www.apracing.com/product_details/road_car_u...
You can download a technical drawing of the caliper here.
http://www.apracing.com/product_details/road_car_u...
http://www.apracing.com/product_details/road_car_u...
You can download a technical drawing of the caliper here.
http://www.apracing.com/product_details/road_car_u...
swanny71 said:
That spec lists the 4-pot calier as having 2 x 38.1mm pistons and 2 x 41.3mm pistons.This gives a total piston area of 4959 mm^2
I understand the rear calipers to be Ford Sierra Cosworth front calipers?
If so, then this link gives some specifications.
http://www.brakepartssuperstore.org.uk/contents/en...
Piston diameter is listed as 39.97mm. But this does not look like single-piston to me.
If it was single-piston of 40mm, then the brake bias without a valve would be 81:19
If it has 2 pistons, then the brake bias without a valve would be 68:32
Maybe that is the wrong brake above?
But for either of those calculations, it does not look like the bias valve should need to do a lot to get the balance right. Given the valve is currently et more than 1/2 way through its range (so should drop 50% of the rear pressure), I would think that the brake bias would be just fine. Unless the front pads or something else is faulty.
Does anybody have better information on the rear calipers or thoughts on the above?
The link and the photo you've got above are both for the front of the 2WD Cossie, which is a 4-pot opposed piston design - very unlikely to be used on the rear of anything as it's very heavy and has no handbrake built in.
Here's what you need to work out the torque from each setup: http://www.stoptech.com/docs/media-center-document...
It's worth noting that with any sliding caliper you double the actual piston area to get the effective area (the sliding actual doubles the clamping force for a given pressure, and doubles the pedal travel as well).
Here's what you need to work out the torque from each setup: http://www.stoptech.com/docs/media-center-document...
It's worth noting that with any sliding caliper you double the actual piston area to get the effective area (the sliding actual doubles the clamping force for a given pressure, and doubles the pedal travel as well).
Edited by Keri on Wednesday 7th November 11:34
Keri said:
The link and the photo you've got above are both for the front of the 2WD Cossie, which is a 4-pot opposed piston design - very unlikely to be used on the rear of anything as it's very heavy and has no handbrake built in.
Here's what you need to work out the torque from each setup: http://www.stoptech.com/docs/media-center-document...
It's worth noting that with any sliding caliper you double the actual piston area to get the effective area (the sliding actual doubles the clamping force for a given pressure, and doubles the pedal travel as well).
That explains why it looks wrong. From Graham Varley's site it says that the rear caliper has been the same from Griffith onwards, and I think it means the Sierra Coswoth rear, which are shown hereHere's what you need to work out the torque from each setup: http://www.stoptech.com/docs/media-center-document...
It's worth noting that with any sliding caliper you double the actual piston area to get the effective area (the sliding actual doubles the clamping force for a given pressure, and doubles the pedal travel as well).
The BCA1346 is mentioned in other Pistonheads threads as the caliper used. As is BCA2060, but that has the same piston diameter as BCA1346 (42.81). My copy of Graham Varley's book is at home so I can check tonight.
42.81 on a sliding caliper, if that doubles the force, gives an effective area of 2879 mm^2 compared to 4959 on the front.
Given the factor of 0.93 from brake disk size gives a 65:35 split.
Looking at the StopTech calculation, my calculations above should be ok. They are working out the torque on each wheel. I am working out the ratio if torque given an equal system pressure and coeefficient of friction.
To get a 75:25 bias from the above setup, given lots of assumptions, the bias valve would need to pass 60% of the brake line pressure. It may be the case that under heavy braking on grippy tyres 25% is still too much rear force and more bias is needed (46% pressure passed to get 80:20).
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