Drum Brakes - Balancing braking effort front to rear.

[PEW]

My apology if this is the incorrect forum for this question but I could find no other threads on brakes elsewhere.

I have a kit car that uses twin leading shoe drum brakes on the front, single leading shoe drums at the rear.

The problem was that the car was over-braked at the front. The front wheels tended to lock very easily. Other owners of this type of car had the same problem, one owner told me was considering fitting a bias valve to limit pressure to the front. I had considered replacing the front drums with discs, to get away from the self servo effect of TLS drums. A lot of work though.

I very recently had the idea of fitting larger diameter rear brake wheel cylinders to increase the effectiveness of the rear brakes. This seems to have worked well, the car now brakes much more effectively without the "front-ended" bias.

The larger cylinders were listed as an alternative part for the car that donated the brakes but it appears, were seldom, if ever, fitted.

Are there any snags with doing this? If so, what should I be aware of? I am aware of the likely increase in rear shoe wear rate but is there something else I have missed? The pedal is fine for both feel and travel.

PW

 

[Peter7307]

PEW,
The only thing I can think of you may need to check is the actual volume of fluid in the reservior and master cylinder ass'y to make sure all the cylinders are well supplied now the rears are larger than before.

If the donor car had this set up as an option it may have had a larger M/C and reservior as well.

Also some makers list the larger items as an "option" to allow the racing teams to get better brakes by using "standard , off the shelf parts" and still remain within the rules of whichever racing catagory is being contested.
Finally there may have been a commercial variant of your donor car which may have needed more robust brakes.

HTH, Cheers, Pete.

 

[PEW]

Hi Pete,

Thanks for your advice, good points.

The master cylinder seems quite large for the size of the braking system, there seems to be a lot of spare capacity so no worries there.

I had to smile at the thought of a racing team. The donor car was actually a Reliant Rialto, a fibreglass 3 wheeler with an 850cc engine and usually bought by old age pensioners! LOL

In truth though, some folks do actually race Reliants on oval speedway tracks. Normally to destruction as they usually roll over on the corners!

Perhaps the bigger rear cylinders were available because there was only one front wheel / brake and no-one could be bothered to climb under the car to service it!

Thanks again

Paul W