Bus handbrake question

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Sat 11 Apr 2009 14:17
Bus handbrake question - spectrafan
Here is something that is puzzling me and maybe any mechanics amongst you can shed some light on it please.........I've been told that the handbrake pressure on a Spectra bus is stronger (better) now, than when it was last tested, the bus is in constant daily use and driven by many different drivers, so is this possible and if so, how?
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Sat 11 Apr 2009 15:46
Bus handbrake question - L'escargot
The handbrake (parking brake) on a modern bus doesn't rely on the strength of the driver. Has something relevant been renewed on the vehicle? What form does the parking brake take, and how is it operated? My guess is that it's operated by compressed air.
www.boschautoparts.co.uk/pdf/3-934584-45-4.pdf
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Sat 11 Apr 2009 20:08
Bus handbrake question - Simon
I'm a bit confused by the question but if we are talking about an Optare Spectra then the hand brake/parking brake will be operated by spring brake pressure rather than air pressure. (Air pressure releases the parking brake hence they are designed to fail safe).

The only way this pressure could be better than when it was last tested is either the brake linings have been renewed or have bedded in now better than last time or the spring brake chambers have been replaced for new ones.

This is of course assuming that the method of testing, presumably a roller brake test is calibrated exactly the same as before. They do vary and it isn't unknown at my local HGV testing station that if your brakes fail by 1% on one test lane, they will send you to the rollers on the other lane just in case that set are a little kinder to you.
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Sat 11 Apr 2009 21:14
Bus handbrake question - Number_Cruncher
>>The only way...

Are there S or Z cams?, slack adjusters?

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