1974 TVR 2500M

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  • Vented Rotor and 4-pot Caliper Swap
    Triumph TR6 and TVR M-Series Cars

    When I started working on ideas for my TVR I decided that I wanted to go fast. Not 200MPH blurred vision fast, but that I wanted a car that stood out. TVR's are pretty unique anyway, so I decided that to do this I was going to need forced induction. It just so happened that I had a Garrett T3 from a Datsun 280ZXT available. Great, so now I should be able to go. What about stopping? After all, if I'm upping the rate of acceleration, I want to make sure that the car still stops.

    One of the resources that has been indispensible in my project has been Lee Janssen's TR6 website. Lee built a very similar engine in a TR6 to what I am planning in my TVR, and also on his site he describes a swap using the stock Triumph solid rotor and Toyota 4-pot calipers. He has a comparison on his site that shows the change in pad size with the toyota calipers, showing the larger surface area that should help reduce brake fade. After reading his site I decided that this was what I wanted to do to my TVR. However, when I talked to some of my friends who have Datsun 280Z's, they warned against keeping the solid rotors as the Z-car guys have problems with them overheating. They suggested that I switch to vented rotors using Datsun 300ZX rotors.

    So, I went and found an article on the 300ZX rotor swap. Unfortunately, further discussion with my datsun friends led to the belief that this would probably not work right. Surely, though, there must be some rotor that works. After all, there are companies in the UK charging exorbitant prices for a vented & cross-drilled rotor w/ 4-pot caliper setup. Fortunately I stumbled across the website of Hugh Barber, which listed one of the mods to his 73 TR6 as "vented front rotors" and another as "4-piston calipers". So, I sent him an email to which he responded:

    The rotors are from a US-spec 1988 Toyota Cressida (front). You need to get a machine shop to open up the inner bore to 3.125". The calipers are from a US-spec 1988 4-cylinder Toyota 4-runner (front). You can see pictures of my installation at:


    Hope this helps,

    Hugh Barber

    Well, that's not bad at all. A quick search on car-part.com found me a pair of rotors in a junkyard, and a pair of calipers in another. Note that I did not use old calipers, nor would I recommend you to use them. These calipers have probably been sitting in the same yard for 10-15 years exposed to the elements. Use them as a core and purchase yourself a rebuilt pair from AutoZone with a lifetime warranty.

    This is a photo comparing the original rotor with the "new" vented rotor. The diameters of the rotors are almost identical, but look at all the extra surface area for radiating heat!

    This photo compares the calipers. Man, those calipers are much larger than the original Girlings.

    To install the calipers you need to ensure that you have the proper caliper mounting bolt. Early TR6's used a 7/16" bolt, while later versions used a 12mm bolt with 7/16" threads. You need this later bolt, which is Moss Motors part number 320-215. You will also need to remake the hard line that goes from the soft line into the caliper as described on Lee's site. Moss lists a part number 588-555 which claims to be a hard line that goes from the hose to a metric caliper, but says that part is unavailable. Perhaps it will be available in the future and would work.

    The calipers come unpainted from AutoZone. To prevent them from looking like the junkyard cores I painted them with VHT brake paint. It has a real nice finish and doesn't seem to scrape off easily. It was also available at AutoZone.