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TR2/3/3A 10" or 9" drums on a TR3A - opinions?

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TR4nut

TR4nut

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10" or 9" drums on a TR3A - opinions?

Aside from originality issues, does anyone see any drawbacks in going with a 9" drum system instead of 10" on a 3A?

I'm cleaning up the various frame and suspension pieces for my 59 3A. The 59 has original 10" brakes in the rear, but as I have a spare straight frame, and a couple of spare differentials with 9" setups my preference is to leave the body on the existing rolling frame and build up the spare frame back to restored rolling status with 9" drums.

I know in doing this I'm sliding away from originality, but what I don't want to slide away from is potentially performance issues - if the 10" are considered superior then I may need to rethink my strategy (despite the apparent lack of 5/8" cylinders!).
 
Re: 10" or 9" drums on a TR3A - opinions?

Performance and originality aside .... I just ordered brake shoes for my TR3A with 10" rear breaks, cost $129. Shoes for the 9" brakes cost $26.

Now while my wife may think an extra 1" is worth $100 ... I don't think so.
 
Re: 10" or 9" drums on a TR3A - opinions?

Parts availability for the 9" setup is <span style="font-style: italic">vastly</span> superior, as you are seeing.

Apparently the performance is superior too -- the 9" setup balances better with the performance of the front brakes than the 10" does.

If I had such easy access to this modification as you do, I'd do it.
 
Re: 10" or 9" drums on a TR3A - opinions?

Hi Randy,

I had the same question awhile back. I too have to make a choice between the 10 Inch and 9 Inch.....My two cars are TS 64870L (9 Inch) and TS 69891LO (10 Inch)....I beleive that they should have both had the 9 Inch.

I am going to go with the 9 inch partly because of the difference in pricing for parts and partly because I have decided to swap the whole rear end out of TS 64 onto TS 69.

Cheers,
M. Pied Lourd
 
Re: 10" or 9" drums on a TR3A - opinions?

There is no concours judge who can ever see if a drum is 9" or 10" diameter behind a steel wheel. It might be more visible with wire wheels.
 
Re: 10" or 9" drums on a TR3A - opinions?

IMO it depends on how your brake balance comes out, with the tires and/or other modifications you make. TS39781LO had been converted to 9" drums with .7" cylinders, and with the wide wheels & sticky tires i was running, the fronts would lock before the rears. Then I replaced the front pads with "non-asbestos", and the balance moved to the rear.

At least for now, I plan to keep the original 10" brakes on TS13571L; but I haven't taken time yet to go try some panic stops.

BTW, getting your old shoes relined is still an inexpensive option. My local FLAPS charged me about $25 for a set of Sports 6 shoes; or TSi will reline them with high performance 'Kevlar' linings for about $50.
 
Re: 10" or 9" drums on a TR3A - opinions?

Oh, forgot to mention (perhaps it's too obvious for words), but the 10" drums are definitely more resistant to fading (all other things being equal), due to the larger surface area. But it takes some pretty hard driving to get even the 9" drums hot enough to fade.
 
Re: 10" or 9" drums on a TR3A - opinions?

The 10" rear drums were swapped to 9" by the factory around car TS56376 after rear wheel locking problems were reported to the factory. It tended to happen in the wet, and more on 48 spoke wire wheeled cars with narrower rims than steel wheel cars. Dunlop RS4 tyres of the era hard a very hard rubber compound, which wouldn't have helped in the wet.

Worn tyres of any make increased the risk of a rear wheel lock up.

The factory reduced rear wheel cylinder bore sizes from car TS34404 to car TS56376 to try and overcome the problem, before making the change to 9" rears.

Of the cars I've had with either 10" or 9" rear drums, one unexpected drawback with the 9" rears is the handbrake is not as good.

Viv.
 
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