35 mm on Vintage 700c road rims

[Never too many bikes]

Hi Guys

I'm stumped and need some input please.

I bought an old Le Jeune road bike for Eroica next year and have just finished the rebuild. 

The bike is running Kenda 700c 35mm tyres on vintage  Wolber TX 700c rims. The tyres and tubes are new and the wheels are in great shape, run true and have no issues. Spokes are flush with nipple head on inside of rim and deeply recessed within  an "aero rim" / deeper dish profile. In other words the spokes are not too long and thus projecting inside the rim. 

 

Day 1 - rode around the block and had a flat on the front wheel. Took the tube out to find what looked like a pinch flat - on the rim side (ie. inside of tube) not the tyre side. So i examined the rim tape - looked okay, but at each spoke hole there was a slight indentation and split.

LBS did'nt have rim tape (said it was'nt really in demand any more) so suggested a couple of layers of electrical tape, which i did (3 to 4 layers).

Fitted another brand new tube (correct size and volume 700c 35 -42mm)and re-fitted tyre.

Just reached 164km since then only to have the front tube let go again - same thing - inside of tube, next to rim, what looks like a pinch flat - in other words long slit running lengthwise on tube. Different place to first puncture.

Strange thing is the rear wheel is same rim, same tyre, same tube and no issues (so far).

 

Any bright ideas as to what is going on?   

[bikebloke]

"                                                        "

 

seriously im not bothering to do this on here anymore ...

[Fat Boab]

From Google the inner rim width is 14mm.

 

Sheldon Brown's chart would suggest 28mm tyre width max is conservative.

 

Probably pushing it with a 35mm.

 

BUT I've run 38mm tyres on a 15mm inner width rim with no problem. And that includes lots of gravel. But I kept the tyres at max pressure which gave a bumpy ride. Not ideal but no punctures.

 

Edit: you mention a long slit on the inner. Wouldn't a pinch flat look like a double hole? A long single (?) slit sounds like a dodgy tube perhaps?

[DJR]

Biggest I've fitted on a rim like that is 32mm and never had a single problem with them. Thoroughly tested it on several Eroicas and on several bikes, both by myself and my 2 sons. No trouble. 

[Never too many bikes]

From Google the inner rim width is 14mm.

 

Sheldon Brown's chart would suggest 28mm tyre width max is conservative.

 

Probably pushing it with a 35mm.

 

BUT I've run 38mm tyres on a 15mm inner width rim with no problem. And that includes lots of gravel. But I kept the tyres at max pressure which gave a bumpy ride. Not ideal but no punctures.

 

Edit: you mention a long slit on the inner. Wouldn't a pinch flat look like a double hole? A long single (?) slit sounds like a dodgy tube perhaps?

Thanks Fat Boab - you're right a pinch would be small holes, kinda in a "V" shape often. so calling it a pinch flat probably did'nt help.

when I got the first flat I had thought that it was a faulty tube and hence just replaced the tube. But the second, which looks also like a slit along the inside of the tube, seems too much like a coincidence to me.

The tyres are being run at their max pressure - 85 and I'm not sure about the casing rolling on corners. The second flat was on the R27 cycle path today, straight and flat - tube let go within 2 or 3 revolutions of the wheel.

The response from Bikebloke makes me think - I had noticed the first flat coincided with a strange ridge on the inside of the tube -almost like it had been folded lengthwise for a section by mistake and then inflated - in fact as I had'nt fitted the tube I had put it down to a poor installation, or tube fault, which led to a premature failure. The slit was along the edge of the ridge. Now that i think about Bikebloke's response I wonder if the narrow rim and the large tyre casings / sidewall / bead are leaving a small gap against the rim, which the tube is pushing into when inflated fully, leading to the strange ridge on the inside and the slit along the ridge? Looking at in cross section, the tyre sidewalls sort of push inwards towards one another, leaving a small inner void, which the tube expands into, causing premature failure along the edge of the void? In other words, normally the tube is round when inflated and nicely seated against the rim, but because of the large tyre has almost a figure of 8 in cross section instead of a circle. The split occuring at the shouder of the lower circle?

When I put the second tube in I partially inflated it so that it has a shape and fits nice and even all the way around (to avoid pinching it on the rim when I put the other side of the tyre on), so i'm more comfortable that the second tube was put in correctly.

 

If the tyre is too big, which makes sense, why is the rear not having the same issues? or perhaps they're still on the way!

[droo]

Are you running the correct width tubes for the tyres, and are you mounting by hand or with a tyre lever?

 

Also, are you making sure the tube isn't trapped between the tyre and rim when mounting?

[DJR]

Are you running the correct width tubes for the tyres, and are you mounting by hand or with a tyre lever?

 

Also, are you making sure the tube isn't trapped between the tyre and rim when mounting?

This sounds like IT

[Fat Boab]

Also think you're on to something here. When I have had punctures with 'over sized' tyres for the rim, I reckon it's been issues with 'quart into a pint pot', and me not paying attention...or just too many pints!

 

 

Are you running the correct width tubes for the tyres, and are you mounting by hand or with a tyre lever?

 

Also, are you making sure the tube isn't trapped between the tyre and rim when mounting?

[HeyYou]

As droo says, tube size!

[Never too many bikes]

Also think you're on to something here. When I have had punctures with 'over sized' tyres for the rim, I reckon it's been issues with 'quart into a pint pot', and me not paying attention...or just too many pints!

 

 

Thanks for the responses guys-

 

Tyre: 700 X 35c

Tube 1 (Came fitted on the bike when purchased from LBS): 700 x 28/32c

Tube 2 (which I fitted): 700 x 35/45c

 

Tubes partially inflated when fitted, so nicely tucked into the tyre.

Fitted by hand ( tyre is big on rim and just slips over).

Both sidewalls checked manually all the way around to ensure no sight of tube.

Inflate to correct pressure.

Ride

Tube split

[Never too many bikes]

Bikebloke - thank you for your response. Not sure if i insulted you somehow and thus caused you to remove your post. If so, i do apologise, was'nt anything intentional.

[DJR]

As droo says, tube size!

I tend to use somewhat undersized tubes. Like 23/25mm tube in a 28 or 32mm tyre. I find them easier to fit and once pumped they work well. 

[Barry_W]

It might seem too obvious but have you run your finger around the inside wall of the rim? There might be a burr or some other sharp damage that’s not visible inside the lip. Also check the inside of the tyre.

[Never too many bikes]

It might seem too obvious but have you run your finger around the inside wall of the rim? There might be a burr or some other sharp damage that’s not visible inside the lip. Also check the inside of the tyre.

Hi Barry,

thanks for your response. I've checked the inside of the rim wall and the tyre. No issues that I can see and both punctures have been in different places - with tube valve in hole and tyre branding at valve stem in both cases,  I've looked at where the punctures occured - one at 11'o clock the other at 3 o'clock.

LBS said it was just bad luck and that I should try again, but this time put some baby powder in the tyre to help the tube settle.

So I've tried again, its getting expensive - so far i've used 3 tubes to do 164km!  

[Butterbean]

How old is the rim tape? And is it perfectly centered?

 

The long slit still sounds like it's pinched during installation, even rubbing will abrade the tube and cause a weakness that's made much worst under inflation?

[Never too many bikes]

How old is the rim tape? And is it perfectly centered?

 

The long slit still sounds like it's pinched during installation, even rubbing will abrade the tube and cause a weakness that's made much worst under inflation?

I took the old rim tape off when I replaced the tube as there were indentations at each spoke hole and a little slit running through each spoke area.

LBS recommended a couple of layers of electrical tape, which i have done. It all feels smooth and clean.

Third tube fitted also punctured! - but this time a tube fault - a small leak where valve connects to the tube, so i'm hoping the LBS will replace the tube as i have proof of purchase from a couple of weeks back and the tube is clearly brand new. 

 

Also looked closely at both split tubes in the sunlight - both have a set of 2 lines (like a railway track) running the entire inner circumference of the tubes. This is made by the little lines (almost like the teeth of comb) which run inside the beading on the tyre - where it sits against the rim.

Both splits are along this line.

 

So i reckon the original response from Fat Boab was right. The tyre is too big for the narrow rim. I'm going to try 28mm as I have some already and see if the problem disapears.

Strange that the back wheel is fine though???