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MG MGB GT V8 Factory Originals Technical - Rear Disc Brakes?

I have just booked my GT V8 into a local diff specialist to have a Borg Warner LSD fitted. While I was there, the workshop guy asked whether I wanted him to fit rear discs as well for an extra $600. That includes fitting a handbrake. I must say I'm tempted but I would be interested to know what other members think, particularly as the majority of the braking effort is done by the front. Tony
Tony

Hi

I can't answer your question as effectively as some of the other members, but I can point you in the right direction.
Check out the the archives where the is lots of information on your question.

Good luck


http://www2.mgcars.org.uk/cgi-bin/gen5

Bruce

Bruce Mills

Tony,

You will no doubt hear that putting rear disc's on your car will not improve the braking as most of the braking is done on the front. I placed rear disc's on the Silver Lady and I did notice a difference. Please check the web page below where I have all the parts that I used.
The down side is that you will have to increase the bore of the M/C to handle the extra piston movement.
I did not use a proportioning valve as the pad size did the work, also the rear caliper has a built in parking brake that I spliced into the MG handbrake. I did the work myself and the approx cost including M/C, used calipers from a junk yard, pads, rotors and brakets was less than US$200.
Good Luck.
Mike

http://www.britishv8.org/MG/MikeCook.htm


Mike Cook

It would be interesting to carry some scientific tests on brake options for B

For interest only as non B

http://www.zeckhausen.com/testing_brakes.htm
Paul

Rear discs have the virtue on a race car of having similar fade characteristics as the front discs do, but for a street car where you aren't (shouldn't) going to be doing repetitive stops from high speeds, they really aren't necessary.

Having said that, the fitting of rear discs seems to be a favourite thing to do for hobbyists, who understandably swear that it made a world of difference. These statements must be tempered by the fact that to admit otherwise would be to admit that they wasted their money.

I've raced and street driven identical cars both with and without rear discs, and it isn't a worthwhile mod unless it simply appeals to you. Disregard the guys that say it really improved things but who started with a crappy poorly maintained drum system and swapped to a new and properly functional disc system - that isn't a true test. I started with perfectly functional rear drums and swapped to perfectly functional discs, and I'm telling you that you needn't bother, and that the drum hand brakes usually work a bit better (and need less attention) than the disc version, dependung on just which rear discs are used (some are better than others in this regard).
Bill Spohn

Mike,

What year is the Prelude that provided rear caliper.

Thanks,

JGC
Jean Guy Catford

Last year at the V8 meet I made a downhill run at the dragon that was fast enough to induce fade in my huge Mach 1 Mustang front brakes (with original type organic pads) but the rear brakes were fine. It's not a matter of braking ability or capacity or fade resistance. But, MG rear brakes require regular adjustment (an easy and quick matter) and servicing is more involved. Disc pads are easy to change and will probably last longer.

If changing the axle I would consider discs, but cost would rule. Either will work fine.

Jim
Jim Blackwood

Jean.
1995 V-tec.
Regards
Mike
Mike Cook

<<Last year at the V8 meet I made a downhill run at the dragon that was fast enough to induce fade in my huge Mach 1 Mustang front brakes>> Yep, I know! I was right behind you and the smell and the smoke really cleared my sinuses. I did notice some fade on mine towards the end of the run but things held together.
Echoing previous comments, I have not experienced any noticeable brake improvement with the rear disc conversion. Mine were converted because of the "cool" factor, the engineering enjoyment and the fact that they came with the Ford axle.
Graham Creswick

I think the rear disk brakes are good for anyone who wants a car for something other then dropping off the kid at school, or getting groceries down the road. To say it's only required for racers is like saying they benefit but only if your a racer which is silly to say the least!

I converted my rears to disk in the restoration. I spent a lot of time working a spreadsheet calculating the loads from the pedals all the way down to the calipers. In the end the larger brakes up front and the smaller brakes in the back came out pretty close. I have brake proportioning valve but it is pretty close as is by design. I have stopped hard in some sand and the front's lock up before the back which is the key. They are very close.

The drums can stop as hard as disk. Some times but you always hear of people with worn or dirty drums that can not get the rears to lock up even on gravel. The problem with drums is they change. The key to good braking is getting the balance just right.

I spent the day working with my Pantera which had a balance bar system on it. The car was dangerous. Would come to a stop sign and it would start skidding. The front's broke way to soon as the backs were not effective. I adjusted the balance, went out and slammed on the brakes. I did it till I cross the threshold where the backs were locking up first. No I didn't leave it there, that is how it should be if you like going backwards when you stop.

Once I found the threshold, I moved it back to where it was slightly front biased. With the little bit of adjusting I did it went from a car which skidded to a stop under easy brake pressure to one that would slam you into the windshield!!! That is the key to good braking.

You cannot get that kind of precision with drums period!

Parking brake? Wilwood spot caliper. Were car guys. It's not hard, this is how I did it:

http://www.rc-tech.net/MGB/em/emn.htm

http://www.rc-tech.net/MGB/suspension/ax.jpg

http://www.rc-tech.net/MGB/

Gary
Gary

Tony,
The final decision is yours of course.

In my opinion the extra price seems high for a BW LSD which , if it is from a Commodore later than a VL , came with discs and an integral drum hadbrake as standard fitting.

I would expect not to pay extra for those.

I agree the key to effective consistent braking is balance and a progressive application (especially in the wet).

To suggest this is not possible with drums is not entirely accurate. It can be done BUT more work is required to keep the stopping ability up to the same hopefully high standard.

Personally I am not in favour of mixing and matching components on which you backside may well depend some day unless you really know what you are doing.

Just one final thought relates to you compliance certificatin (engineers certificate as it is know here in Victoria).
You may need an extra check on this if ANY changes to the braking system are carried out.

Pete.

Peter Thomas

<<the smoke really cleared my sinuses.>>
Yeah, and your passenger got some really wild video that I still need to get a copy of. But y'know, the only reason I was in front is cause you guys let me go by.

If you run the stock rear brakes you have to adjust them periodically. Either way you have to service them when needed. Can't let it slide and then complain they didn't work.

It's a fact that either type have certain advantages and disadvantages. Disc brakes replaced drums on things like dirt bikes for a reason, they are lighter and have better feel because the drum brakes rely on self actuation which takes away some of the "touch". But they both work. If I was swapping axles I'd try to go with discs, but I'd look for something with a reasonable cost and to me $600 seems a little steep. But then I don't feel that I can afford Wilwood, I'd rather put the money in the engine or tranny so I look for other ways.

Jim
Jim Blackwood

Tony has a good Saab setup from parts scavenged. I think he has minimal expense in his. I don't know what the balance is.
Gary

This thread was discussed between 22/02/2007 and 24/02/2007

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