Vibration under breaking

[Chris]

I have a 97 4.2 with 12k miles on the clock - it's my first TVR, and I'm in love. Previously had Porkers (last was a Boxster S, but wanted something cheaper and more entertaining). Smiles per pound makes the second hand Cerbie an absolute bargain, and when I put my foot to the floor, I sometimes think they shouldn't be allowed on the road!!!

Anyway, I've run into my first (minor) problem. There is a lot of vibration at the steering wheels when I break fairly firmly from highish speed (no troubles at lower, say below 60, speeds).

Any ideas what's causing it - saw an interesting post on here (I think) that said warped break discs were an old wives tale, and that the warped disc sensation was actually caused by break pad deposits stuck on the disc.

It may be this, or something else. Any ideas?

Prior to me buying the car a month ago the car sat largely unused for 12 months, and before that, only averaged about 2.5k a year - not sure if this has any bearing.

Cheers.

[P7ULG]

Might be an idea to get the disc skimmed or even renewed and change the pads.From experience thses cars don't like standing unused,

[domster]

Check wheel balancing, too.

[M@H]

Hi,

quote: saw an interesting post on here (I think) that said warped break discs were an old wives tale, and that the warped disc sensation was actually caused by break pad deposits stuck on the disc.

with the ustomst respect to all concerned, this does sound like bx to me ..I have checked the runout on discs in the past to look at the warping and have never seen any deposits on them.. aterall how many "in-use" brake discs do you see that aren't just bright worn metal, I've never seen "patches" of anything on them. (barring rust spots after rain)

Sounds classically like warped discs to me... get a wheel off and stand an axle stand either side of the disc, put a sharp pencil (or anything similar) on top of each with the points pushed up to the disc surface, then spin and see cheers, Matt.

[GreenV8S]

quote:

with the ustomst respect to all concerned, this does sound like bx to me ..I have checked the runout on discs in the past to look at the warping and have never seen any deposits on them.. aterall how many "in-use" brake discs do you see that aren't just bright worn metal, I've never seen "patches" of anything on them. (barring rust spots after rain)

Sounds classically like warped discs to me... get a wheel off and stand an axle stand either side of the disc, put a sharp pencil (or anything similar) on top of each with the points pushed up to the disc surface, then spin and see cheers, Matt.

Each to his own, but having read the article it was clear that Carole Smith knew an awful low about metallurgy and the mechanics of pads rubbing on discs. He explained in detail how brakes work in different conditions, and exactly how it went wrong. His explanation was completely convincing, and also explained why brakes could 'warp' for no apparent reason without having been mistreated in any way. I think he was right on the money.

If you want to read the full article yourself, you can find it here:

www.stoptech.com/whitepapers/warped_rotors_myth.htm

Cheers,
Peter Humphries (and a green V8S)

[M@H]

Well I never did... !! a most fascinating read.

OK partial apologies then.. however I still maintain that warped discs are a reality, and have seen the runout on the solid discs on the beetle.. Afterall an uneven heat distribution on any metal will cause it to bend won't it.. !?

[phockit]

Just had my second set of replacement disks due to "warping". Manifests itself as a strong and rapid vibration through the steering wheel under normal (medium) braking. Really stamp on the brakes and you don't get the vibes. Typically didn't feel anything the first time I used the brakes either, i.e. only apparent when there's some heat built up.

Now had my disks replaced with a later version from the Tuscan (not the drilled ones), apparently they've got different venting to stop the recurrent problems with the originals.