Ivaan Posted November 6, 2011 Share Posted November 6, 2011 One thing I've really noticed about the R1 BEC is it's comparitively poor stopping ability. Compared to my old K series car, it just doesn't pull up. I could stand the old car on it's nose under braking before locking up. The BEC is a live axle car, with drums on the rear and 4 pot calipers on the front with vented discs. I'm currently running AO48's, but have the same problem with CR500s and R888s. The problem is particularily noticeable in damp / wet conditions. The spring rates and dampers are lightweight to suit the car, as built by Ferrino. The car was set up and corner weighted during the re-build before I bought it. It's easy to lock all four wheels. It feels as if the lack of the heavy lump at the front, means there's little loading on the front wheels under braking. I've already set the dampers to a very soft setting, and use 16psi tyre pressure, to enduce a front end dive, but the car stays fairly flat. I don't think it's brake material or biased related. Will raising the back, increasing the rake help the balance? ( It's set around the standard 15mm rake at present.) Do other BECs suffer from this? Thanks for any advice, Clive Link to comment Share on other sites More sharing options...
CaterBram Posted November 6, 2011 Share Posted November 6, 2011 Ivan, Are you sure all 4 are locking up or just the front's, recently upgraded the rear cylinders on my live axle and have had a noticable improvement in braking. originals were 5/8" the new ones are 3/4", alway's had very cool rear brakes regardless of how much hammer they got, now they get nice & warm when driven hard and the 7 stops much quicker. Link to comment Share on other sites More sharing options...
blade_runner Posted November 6, 2011 Share Posted November 6, 2011 My blade, with Alcon 4 pots, Pagid RS4 pads and solid drilled discs on the front, with ital rear disc conversion, solid drilled motorbike discs, ford single pot calipers, and Ferrodo DS2000 on the rear and an AP race master clyinder pulls up on a sixpence on track when warm seems to out brake most things and doesnt seem to suffer any brake fade or pedel travel, I'm more than happy with my set up. Link to comment Share on other sites More sharing options...
blade_runner Posted November 6, 2011 Share Posted November 6, 2011 Forgot to add, I originally had Ferrodo pads on the front of the car then after the winter lay up this year got the car out and almost had an accident as the fronts were locking at quite light pedel applications, after speaking with Performance Braking in Monmouthshire, they suggested that the pads being old but only half worn has absorbed moisture and swelled and changed shape and were grabbing the disc, I borrowed an old set of EBC green stuffs off a friend, fitted them and no more locking up! so knew the pads were at fault. spoke to Performance braking again and the original ferrodo's were no longer available, so the suggested the Pagid RS4's and I must say they are fantastic, the only set back is a little low speed squeal. Link to comment Share on other sites More sharing options...
Revin Kevin Posted November 7, 2011 Share Posted November 7, 2011 Clive I agree with all of the above, particularly (if the pads etc are good and you are getting front wheels only locking) with caterbram. the Ital drums with the standard 5/8 cylinders are underbraked. As caterbram says going to 3/4 cylinders helps and probably the front four pots brakes you have are a bigger piston area than the standard brakes which will exasperate this inbalance. The 3/4 cylinders should help, disc brake conversion would be even better along with bias braking to fine tune the balance. Rake should not have any effect. Cheers Chris Edited by - Revin Kevin on 7 Nov 2011 18:46:23 Link to comment Share on other sites More sharing options...
Ivaan Posted November 7, 2011 Author Share Posted November 7, 2011 Thanks for all the advice and information. It could be the fronts overbraking, with the uprated 4 pot calipers causing lock ups before the rears have any real effect. However, it does feel as if the front wheels don't load up enough to push the tyres into the road. On my old K series Dedion Roadsport, with Standard brakes and Mintex 1144 pads in the front, it would really dig into the road under braking. I'll have to do some testing with an observer watching / videoing, to see exactly what is happening under braking. If I can find a suitable location and a couple of volunteers, I may try to do some testing with other 7s comparing stopping distances. I'll have to contact Nick Chan to find out what pads are in the front. Caterbram - Searching Techtalk, I see 3/4" Girling cylinders available for £14 ea + VAT, from PowerTrack Ltd. Got to be worth a try. Can you get different grades of brake shoes? Blade Runner - I'm interested in the rear disc upgrade you've done. Are there further details somewhere? Cheers. Clive Edited by - Ivaan on 7 Nov 2011 20:09:34 Link to comment Share on other sites More sharing options...
blade_runner Posted November 7, 2011 Share Posted November 7, 2011 Ivaan, just a thought, are the rear brakes on your car adjusted ok? if the caterham system is split front rear, and the rears need adjusting, it would create pedel travel for the rear circuit, and maybe by this time the fronts are locking? I maybe talking crap, but worth checking the rear shoe adjustment via the square nut on the drum back plate, and checking the resistance required to turn the drum. As to my rear disc conversion... it came with the car, James whiting used to make a rear disc conversion for the Ital axle, but i think unless you can get a few people interested he's not interested in making only one kit up. might be worth contacting him. I spoke to james earlier in the year as I thought Id source some new discs for my rears, but it turns out I have a one off prototype rear disc conversion, he fitted it to my prototype car, and then went in another direction with the conversion, and He cant remember which Motor bike the discs came off of! the later kit used standard solid rear disc's as fitted to the De dion. My car also has been converted to the Ford PCD front and rear. there are pics of my rear discs on my webshots, just click the link at the bottom. Link to comment Share on other sites More sharing options...
blade_runner Posted November 7, 2011 Share Posted November 7, 2011 Edited by - blade_runner on 7 Nov 2011 23:03:35 Link to comment Share on other sites More sharing options...
Revin Kevin Posted November 8, 2011 Share Posted November 8, 2011 Clive, Questmead will re line your brake shoes with uprated material, this wont give you any more braking effort as the coeffcient of friction is approximately the same but the material will deal with more heat before fading. Cheers Chris Link to comment Share on other sites More sharing options...
Ivaan Posted November 8, 2011 Author Share Posted November 8, 2011 Cheers all. Somewhere in the back of a dusty cupboard in my garage I think I've still got the adjustment tool for drum brakes...not been used in donkeys years - probably on my Superminx. I think I'll whip the drums off, check everything and clean, then adjust and see if there's any improvement. Then upgrade to the 3/4 cylinders and see how we go....or stop. Clive Link to comment Share on other sites More sharing options...
Ivaan Posted November 13, 2011 Author Share Posted November 13, 2011 Over the weekend, I've inspected and pulled up the rear brakes - all good. I've just been out testing and trying to see what exactly is happening. The fronts don't give much peddle feel for the lock up point, and even at low speeds suddenly lock, especially if it's damp. The braking effort is too low. I think the front brakes are too powerful for such a light car. Does that make sense?. I'll fit some 3/4" rear cylinders and see how it feels. Clive Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted November 13, 2011 Area Representative Share Posted November 13, 2011 Clive, 'didn't get chance to have a chat yesterday.. Don't under estimate how much of the stopping power comes from the rear brakes. Your old car, with stanard brakes with 1144's in the front, and standard rear will have had good balance, and the rears will have been working pretty hard. When I modified my pedalbox to use twin master cylinders and a bias bar, I proved how much the rears add to the stopping power! I'd try the 3/4" rear cylinders, but be very careful when you're testing it. When the rears are locked, the car can swap ends very easily! Going from 5/8" to 3/4" is quite a big move (almost half as much power again). Are any other sizes available? Link to comment Share on other sites More sharing options...
James_Russell Posted November 13, 2011 Share Posted November 13, 2011 I have the same chassis and rear brakes as you, so I feel qualified to offer a couple of points. For me, 3/4" rear cylinders are obligatory. Even with standard front brakes and 3/4" rear cylinders I feel that the rear brakes are lacking- I can only imagine how much this would be exaggerated with the big brakes on the front. If you have very aggressive pads in the fronts, pagid for example, I can imagine they'd be grabbing before the pedal pressure is great enough to really get the drums working. For a start, my drums get removed regularly to get all the dust out. They also get adjusted very regularly. This minimises dead travel so that you can get the pressure on quicker. Compensating with rake and tyre pressures can't be good, particularly on a car which has been corner weighted. When I had too much rake I was getting a very fun but very slow lift-off oversteer, to the point that I was having armfuls of opposite lock before the apex at paddock. I'm not convinced by rear disc conversions to improve stopping power. Pedal feel, maybe- but unless you can't lock the rear brakes I can't see it actually improving stopping power. Link to comment Share on other sites More sharing options...
4ster Posted November 13, 2011 Share Posted November 13, 2011 Clive I have no experience with a BEC - but plenty with front wheels locking on a (sort of) standard car - live English axle with discs. After fiddling about with pad materials and cylinder sizes (and talking to Richard Price who has a lot of sensible advice to give on the subject – and most things actually!) I settled on limiting the power to the front brakes via the bias bar/cylinder sizes and, most importantly, the pad material. After all sorts of Pagid compounds, I went back to Mintex 1144. It is now very difficult, but not impossible, to lock the fronts and the braking is really good – with the rears doing far more work than before. It seems to be a case of finding the right balance for your car but my experience would suggest that having aggressive front pads is not a good starting point. I get the impression that you aren’t exactly clear what yours are – check this out first. Link to comment Share on other sites More sharing options...
CaterBram Posted November 14, 2011 Share Posted November 14, 2011 I've got 1144's on the front, 3/4 brake cylinders on the rear, the stopping improvement is noticable and so far the front's do still lock first. might be worth putting new brake shoes in as well so they can be bedded in at there new operating temperature. Link to comment Share on other sites More sharing options...
Ivaan Posted November 14, 2011 Author Share Posted November 14, 2011 Thanks for all the replies. I've just bought 2 No 3/4" cylinders from the first place I tried. After the first comment "Ital ! Haven't erd of them for years", he disappears in the back and comes out with two...... cash price £14 for the pair. Apparently, they're for the Marina. 😬 If I can get the braking right, this is going to be a brilliant car. Clive Link to comment Share on other sites More sharing options...
Ivaan Posted November 14, 2011 Author Share Posted November 14, 2011 Started to swap the cylinders over, but they look the identical. There's no part nos on them. I've just been on Quinton Hazell website. One is 17.5mm, the other 19mm, so I guess they'll look pretty similar. Will it only be the internal piston sizes that are different, or should I be able to see / measure any size differential? I just don't know the size of the one's currently on the car. Clive Link to comment Share on other sites More sharing options...
James_Russell Posted November 14, 2011 Share Posted November 14, 2011 They shouldn't look any different except the piston diameter Small increase in diameter, maybe, but the difference in cross sectional area is probably quite significant... Link to comment Share on other sites More sharing options...
6speedmanual Posted November 14, 2011 Share Posted November 14, 2011 Yes, they look the same externally. If you peel back the dust boot you can mic the piston diameter to check. Peter Ps. Thinking about this thread, it is quite easy to work out the load transfer under braking. Will give you idea of the propotion of brake firce needed at each end. You soften of springs etc may give you fractional weighr distribution changes. Load transfer not much affected. P Link to comment Share on other sites More sharing options...
Gridgway Posted November 14, 2011 Share Posted November 14, 2011 You need to know the height of the centre of mass to work out the load transfer under braking. However, I'm not sure how that helps you with fronts being disks and rears being drums. Link to comment Share on other sites More sharing options...
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