GSB's Whyte PRST-4 build
- Thread starter GSB
- Start date
Good lord, I recognise that bike fotorat, it’s been a long standing resident on eBay for a good while, no? Very original finish on that frame btw :thumbsup:
Right, spherical bearings. To save time I’m going to cut an paste the contents of an email I sent to a member here who bought one of my PRDt-4’s.
“Creaks, rattle and general play are part of Preston life, but the PBA10 spherical bearing is a special pain in the backside. The basic issues are these;
on some frames, the fit of the bearing into the lower suspension arm is a bit slack. This can be rectified with shim material wrapped around the outside of the bearing. Anything from 0.05mm shim steel down to single wrap of tinfoil or just a perfect fit, depending upon how steady the drill operators hand was when he made your frame.
The other more usual problem with them is that you can get cheap PBA10’s, and you can get good PBA10’s, but you don’t get good cheap ones. You definitely get what you pay for. Same goes for the rest of the bearings, which were actually designed for, and are more usually found in the control surfaces of light aircraft.
The PRST requires a good bearing. This is due to the fact that with this frame design the bearing is being loaded in the ‘wrong’ direction. Braking loads are applied laterally, in the direction the bearing is designed for, but the riders weight and all the suspension loads are borne axially, effectively trying to push the ball sideways out of its cage. The bearing can do this, but it’s the weakest part of its capability. Any wear or deformation between the ball and the cage will be invisible with load on the bike, but as you’ve found, when unloaded the ball will rattle around in the cage. This might be because the manufacturers tolerances are yards wide, or it might be because the materials are to soft and have deformed with use.
As for where to get a decent one? You’re testing my memory now, so I’ve referred back to a post I put on MTBR ages ago when I decided to track down a ‘once and for all’ fix for my bike.
“The joker in the pack is the spherical bearing in the steering. It's a plain spherical bearing type PBA, size 10. However, there's a multitude of manufacturers, materials, and load ratings.
Buy a cheap one and you'll get 6 weeks out if if you're lucky. The loading on the bearing is in the "wrong" direction, so it needs to be something special. I will be using flouro.de bearings in my bikes this year. The standard series PBA10 "GL" can cope with 7.5kN of axial load. That should be plenty, but sadly the cheaper bearings seem to fail due to the grit and crud that gets in them. The "GLRSW" spec is made from stainless steel, and is rated for loads over three times higher. “
So, a full stainless bearing with a very high axial load rating is the way forward, along with a low coefficient of friction.”
Now, the member in question was Mike, aka ‘Velofrog’ and be recently fitted one of these more exotic bearings to his bike, and I believe it cost the princely sum of about £35.
As for your rubber gaiters on your JW2, they look like they might be aftermarket/custom made. It would be really helpful for indentification and recreation if you could strip it down and photograph the parts in detail. The exact same parts could be sourced using the dimensions and markings.
Right, spherical bearings. To save time I’m going to cut an paste the contents of an email I sent to a member here who bought one of my PRDt-4’s.
“Creaks, rattle and general play are part of Preston life, but the PBA10 spherical bearing is a special pain in the backside. The basic issues are these;
on some frames, the fit of the bearing into the lower suspension arm is a bit slack. This can be rectified with shim material wrapped around the outside of the bearing. Anything from 0.05mm shim steel down to single wrap of tinfoil or just a perfect fit, depending upon how steady the drill operators hand was when he made your frame.
The other more usual problem with them is that you can get cheap PBA10’s, and you can get good PBA10’s, but you don’t get good cheap ones. You definitely get what you pay for. Same goes for the rest of the bearings, which were actually designed for, and are more usually found in the control surfaces of light aircraft.
The PRST requires a good bearing. This is due to the fact that with this frame design the bearing is being loaded in the ‘wrong’ direction. Braking loads are applied laterally, in the direction the bearing is designed for, but the riders weight and all the suspension loads are borne axially, effectively trying to push the ball sideways out of its cage. The bearing can do this, but it’s the weakest part of its capability. Any wear or deformation between the ball and the cage will be invisible with load on the bike, but as you’ve found, when unloaded the ball will rattle around in the cage. This might be because the manufacturers tolerances are yards wide, or it might be because the materials are to soft and have deformed with use.
As for where to get a decent one? You’re testing my memory now, so I’ve referred back to a post I put on MTBR ages ago when I decided to track down a ‘once and for all’ fix for my bike.
“The joker in the pack is the spherical bearing in the steering. It's a plain spherical bearing type PBA, size 10. However, there's a multitude of manufacturers, materials, and load ratings.
Buy a cheap one and you'll get 6 weeks out if if you're lucky. The loading on the bearing is in the "wrong" direction, so it needs to be something special. I will be using flouro.de bearings in my bikes this year. The standard series PBA10 "GL" can cope with 7.5kN of axial load. That should be plenty, but sadly the cheaper bearings seem to fail due to the grit and crud that gets in them. The "GLRSW" spec is made from stainless steel, and is rated for loads over three times higher. “
So, a full stainless bearing with a very high axial load rating is the way forward, along with a low coefficient of friction.”
Now, the member in question was Mike, aka ‘Velofrog’ and be recently fitted one of these more exotic bearings to his bike, and I believe it cost the princely sum of about £35.
As for your rubber gaiters on your JW2, they look like they might be aftermarket/custom made. It would be really helpful for indentification and recreation if you could strip it down and photograph the parts in detail. The exact same parts could be sourced using the dimensions and markings.
fotorat1
Retro Guru
Cheers I was hoping someone knows the dimensions so that I can order one - no worries though I will get mine out to measure it - although I was planning to use the bike daily while it came, never mind.
http://fluro.de/index.php/en/products/s ... ec-niro-ms
http://fluro.de/index.php/en/products/s ... ec-niro-ms
fotorat1
Retro Guru
Nice one
Outer = 26mm
Shaft = 10mm
ball width = 14mm
Housing width 10.5 fluro vs 9.5 dunlop JBS 10N
This must be the rubber I have on my JW2:
http://www.bearingshopuk.co.uk/bearings ... meter=3841
Outer = 26mm
Shaft = 10mm
ball width = 14mm
Housing width 10.5 fluro vs 9.5 dunlop JBS 10N
This must be the rubber I have on my JW2:
http://www.bearingshopuk.co.uk/bearings ... meter=3841
fotorat1
Retro Guru
this one looks good:
its says dynamic load Co 10KN
and Static Load cor 25KN
https://simplybearings.co.uk/shop/p1517 ... _info.html
its says dynamic load Co 10KN
and Static Load cor 25KN
https://simplybearings.co.uk/shop/p1517 ... _info.html
