Wheels,Tyres & Security Bolts.

eugenepm43 · Post by **eugenepm43** » Mon Apr 25, 2011 6:40 pm

I have a 1960 G12 CSR fitted with Dunlop 19" alloy wheels WM2 rims.

1.What size tyres should be fitted & what is recommended from riders experiences?
Front:- 3.25 x 19 or 3.60 x 19. Rear:- 3.50 x 19 or 4.10 x 19.
2.Do I need security bolts with modern tyres? i.e. Speedmaster, Safety Mileage or Dunlop TT 100's.
3.If security bolts are to be fitted: front & rear wheels or is the rear wheel only required.
4. Also is it usual to fit two security bolts to a wheel for a good balance?
I am not a "speed king" or a "foot rest scraper". 60 mph is good enough with the odd 70 mph burst to blow out the cobwebs.

bjork · Post by **bjork** » Mon Apr 25, 2011 7:38 pm

Welcome to the website Eugene, those tyre sizes are the same-i.e. 3.60=3.25 in old money and 4.10=3.50.
The security bolts aren't really necessary unless you ride a lot off road and with lower pressures. They aren't likely to creep under normal road conditions without them and it makes wheel balancing easier too.
Hope that helps,

Steve.

Duncan · Post by **Duncan** » Mon Apr 25, 2011 11:56 pm

Eugene, modern tyres also need to be run at a higher pressure than you will find quoted in the handbook. As for tyres sizes you can also consider 90/90x19 front or 100/90x19 rear.

eugenepm43 · Post by **eugenepm43** » Wed May 04, 2011 8:28 pm

I asked these questions as I recently had new tyres fitted.
The rear was originally a 4.10 x 19 and a 3.50 x 19 Avon SM was fitted; no security bolt fitted either time.
After about 270 miles since the renewal, the tyre turned on the rim and pulled out the valve. Not good for the old ticker!! Pressure cold was 30 psi prior to going for a run.
A new tube with one security bolt to wheel was fitted then. After about another 150 miles tyre went flat very quickly whilst being ridden, and guess what, the tyre had turned on the rim!
The valve had not pulled out but the tube was punctured. I hope this is just a run of bad luck.
Have now made sure the rim insides are clean and the tyre fit/rim area is clean. A new tube and two security bolts will be fitted and fingers crossed.

SPRIDDLER · Post by **SPRIDDLER** » Wed May 04, 2011 9:01 pm

I find 30 psi solo a bit harsh on the arms and nethers so use 24 front and 26 rear unless loaded with gear then I go up a couple of psi in both. Waddever...
Strikes me you had a spoke head, grit, flaky chrome or rust abrading the tube and the tube turned as it deflated.
It would also be worth checking the accuracy of your tyre gaugeEdited by - SPRIDDLER on 04 May 2011 8:02:31 PM

1608 · Post by **1608** » Wed May 04, 2011 10:43 pm

I don't think the tyres moved on their rims before the punctures, only afterwards. I may be wrong but I thought security bolts were only needed if you were running on low tyre pressures for trials work. I was also advised that the valve securing nut should be left loose so that in the event of a puncture the valve has some movement and hopefully not get ripped out, could be wrong though!.

SPRIDDLER · Post by **SPRIDDLER** » Wed May 04, 2011 11:41 pm

I wouldn't know if my tyre had moved on the rim since I don't record its position to start with.
I too leave the valve securing nut undone a few turns. I've had only two punctures (both rear wheel ones) in 30k miles (6 new tyres) and not had a valve pull out. Yet.

ianselva · Post by **ianselva** » Thu May 05, 2011 10:03 am

Having had two very scary rides after rear punctures , I am very much in favour of security bolts and always fit one in the rear. Both times a puncture in the rear caused a rapid deflation which resulted in the tyre turning and ripping the valve out. Now I also back off the valve securing nut to lock up against the valve cap to give a bit more movement in case the tyre moves again.
OTT perhaps ,but I don't want another ride like that.

Ian

Janet · Post by **Janet** » Thu May 05, 2011 1:29 pm

I don't have security bolts on any of my bikes ( not sure I know what they look like ) and I don't recall having any tyres move on the rim. I do keep them well blown up, though, to suit the recommendations of the modern day tyre manufacturer. Generally, tyres today have softer sidewalls so tend to flex more with lower pressures when cornering with my knee down.

Note: part of the above may be a little generous with the truth.

MikeM. · Post by **MikeM.** » Sun May 08, 2011 11:28 pm

Is that what you were doing on the muddy lane on the Westward Ho! Janet?
Did you get to the bottom of the Peter's e-mail regarding his picture on the 'HO!?