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Wide tire on narrow rim?



 
 
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  #1  
Old September 9th 16, 10:48 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default Wide tire on narrow rim?

A friend asked me to resurrect his 1980s Trek road bike. It's a nice,
classic 531 steel frame bike. He'd stashed it in his basement well over
15 years ago because he was afraid of riding its narrow tires and rims
on our notoriously rough roads. He's been riding his mountain bike on
the roads ever since.

And indeed, when he brought the Trek over, the rear wheel had a broken
spoke and was badly out of true, and it had a flat spot that looked like
a pothole impact. I fixed that and several other minor problems.

We're at the point where he needs to choose tires. He'd like something
wider than the 27 x 1" tires he had mounted (and one of their beads
looks suspicious anyway). But the Rigida rims measure only 12.5 mm
inside width, and the charts I can find online recommend tires no wider
than 25mm or 1".

So, how risky is violating that limit? I'd consider fitting Panaracer
Paselas in a 1 1/8" width if it's reasonable, but I don't want to get
the guy into trouble.

BTW, I doubt I can get him to spend for a new wheel set. And his
Dia-Compe "G" single pivot side pull brakes are at the limit of their
60mm drop, so moving to 700c wheels would require new brakes, or at
least some antique drop bolts.

Again, in summary: Are 1 1/8" tires on 12.5mm rims likely to work? How
risky is that?

--
- Frank Krygowski
Ads
  #2  
Old September 9th 16, 10:56 PM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default Wide tire on narrow rim?

On 9/9/2016 4:48 PM, Frank Krygowski wrote:
A friend asked me to resurrect his 1980s Trek road bike.
It's a nice, classic 531 steel frame bike. He'd stashed it
in his basement well over 15 years ago because he was afraid
of riding its narrow tires and rims on our notoriously rough
roads. He's been riding his mountain bike on the roads ever
since.

And indeed, when he brought the Trek over, the rear wheel
had a broken spoke and was badly out of true, and it had a
flat spot that looked like a pothole impact. I fixed that
and several other minor problems.

We're at the point where he needs to choose tires. He'd
like something wider than the 27 x 1" tires he had mounted
(and one of their beads looks suspicious anyway). But the
Rigida rims measure only 12.5 mm inside width, and the
charts I can find online recommend tires no wider than 25mm
or 1".

So, how risky is violating that limit? I'd consider fitting
Panaracer Paselas in a 1 1/8" width if it's reasonable, but
I don't want to get the guy into trouble.

BTW, I doubt I can get him to spend for a new wheel set.
And his Dia-Compe "G" single pivot side pull brakes are at
the limit of their 60mm drop, so moving to 700c wheels would
require new brakes, or at least some antique drop bolts.

Again, in summary: Are 1 1/8" tires on 12.5mm rims likely to
work? How risky is that?


Other Trek models then, and many other bikes, came with
Rigida 1319 or 1320 and 27 x 1-1/8 tires stock. It's not
only theoretically OK, it was a once-popular combination in
huge volumes. Not to worry.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #3  
Old September 9th 16, 11:41 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Posts: 10,422
Default Wide tire on narrow rim?

Don't know anything about rims as narrow as 12.5mm, but for several months, when components took 6-8 weeks to arrive, and then I was too ill to work on the bike, I rode with a 60mm tyre on a rim with only 16mm inside width. The theoretical maximum tyre width on this rim is 40mm, so a 50% tyre to rim overmatch. The wheel so shod carried a high torque motor, so it wasn't mollycoddled. I did 6000km and change (about 3600m) on this combination before a proper Exal XL25 rim with 25mm between beads could be fitted. The narrow rim showed no visible damage when it was removed.

I rode this combo no differently from fat tyres on fat rims. Almost all the effects were subtler than I expected. Comfort suffered slightly; I didn't in fact increase pressure to make the ride harsher (often said to be required with narrower rims) but there was a small amount of sway in the steering as the tyre squished a bit more, and this was at first disconcerting, making me warier and therefore less comfortable on the bike; its net effect over the long term was nil, but at first it made me uncomfortable cornering at the same speed as before. There was no visibly faster tyre wear on the narrow rim; and the rear tyre (on a correctly sized rim) still wore faster than the front tyre, even though the front was carrying at least some of the drive.

Fat tyres on correct-width rims are, by the same token, subtly more confidence-inspiring. With my fat tackies once more shod on fat rims, I no longer hesitate slightly before turning the bike in at speed on the twisty downhills around here.

I conclude from this experience that those ERTRO "recommendation" are cover-your-ass numbers with big margins available for intelligent interpretation, at least at the balloon end of the spectrum and with best quality components. It is of course possible that at the narrow end of the tyre spectrum the margins available for interpretation may be narrower.

The current theory (last time I looked, anyway), is that a 12mm rim should be able to carry a tyre up to 30mm wide within the "rules". 1-1/8in tyre is only 28.6mm wide. Unless this fellow is a reckless downhill charger, I'd be tempted to try a pair of 32mm tyres.

Andre Jute
Big Balloons

On Friday, September 9, 2016 at 10:48:45 PM UTC+1, Frank Krygowski wrote:
A friend asked me to resurrect his 1980s Trek road bike. It's a nice,
classic 531 steel frame bike. He'd stashed it in his basement well over
15 years ago because he was afraid of riding its narrow tires and rims
on our notoriously rough roads. He's been riding his mountain bike on
the roads ever since.

And indeed, when he brought the Trek over, the rear wheel had a broken
spoke and was badly out of true, and it had a flat spot that looked like
a pothole impact. I fixed that and several other minor problems.

We're at the point where he needs to choose tires. He'd like something
wider than the 27 x 1" tires he had mounted (and one of their beads
looks suspicious anyway). But the Rigida rims measure only 12.5 mm
inside width, and the charts I can find online recommend tires no wider
than 25mm or 1".

So, how risky is violating that limit? I'd consider fitting Panaracer
Paselas in a 1 1/8" width if it's reasonable, but I don't want to get
the guy into trouble.

BTW, I doubt I can get him to spend for a new wheel set. And his
Dia-Compe "G" single pivot side pull brakes are at the limit of their
60mm drop, so moving to 700c wheels would require new brakes, or at
least some antique drop bolts.

Again, in summary: Are 1 1/8" tires on 12.5mm rims likely to work? How
risky is that?

--
- Frank Krygowski

  #4  
Old September 10th 16, 12:32 AM posted to rec.bicycles.tech
John B.[_6_]
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Posts: 2,202
Default Wide tire on narrow rim?

On Fri, 9 Sep 2016 17:48:42 -0400, Frank Krygowski
wrote:

A friend asked me to resurrect his 1980s Trek road bike. It's a nice,
classic 531 steel frame bike. He'd stashed it in his basement well over
15 years ago because he was afraid of riding its narrow tires and rims
on our notoriously rough roads. He's been riding his mountain bike on
the roads ever since.

And indeed, when he brought the Trek over, the rear wheel had a broken
spoke and was badly out of true, and it had a flat spot that looked like
a pothole impact. I fixed that and several other minor problems.

We're at the point where he needs to choose tires. He'd like something
wider than the 27 x 1" tires he had mounted (and one of their beads
looks suspicious anyway). But the Rigida rims measure only 12.5 mm
inside width, and the charts I can find online recommend tires no wider
than 25mm or 1".

So, how risky is violating that limit? I'd consider fitting Panaracer
Paselas in a 1 1/8" width if it's reasonable, but I don't want to get
the guy into trouble.

BTW, I doubt I can get him to spend for a new wheel set. And his
Dia-Compe "G" single pivot side pull brakes are at the limit of their
60mm drop, so moving to 700c wheels would require new brakes, or at
least some antique drop bolts.

Again, in summary: Are 1 1/8" tires on 12.5mm rims likely to work? How
risky is that?


See Sheldon's article http://www.sheldonbrown.com/tire-sizing.html
and note just below the red and green chart.
--
cheers,

John B.

  #5  
Old September 10th 16, 03:46 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default Wide tire on narrow rim?

On 9/9/2016 5:56 PM, AMuzi wrote:
On 9/9/2016 4:48 PM, Frank Krygowski wrote:
A friend asked me to resurrect his 1980s Trek road bike.
It's a nice, classic 531 steel frame bike. He'd stashed it
in his basement well over 15 years ago because he was afraid
of riding its narrow tires and rims on our notoriously rough
roads. He's been riding his mountain bike on the roads ever
since.

And indeed, when he brought the Trek over, the rear wheel
had a broken spoke and was badly out of true, and it had a
flat spot that looked like a pothole impact. I fixed that
and several other minor problems.

We're at the point where he needs to choose tires. He'd
like something wider than the 27 x 1" tires he had mounted
(and one of their beads looks suspicious anyway). But the
Rigida rims measure only 12.5 mm inside width, and the
charts I can find online recommend tires no wider than 25mm
or 1".

So, how risky is violating that limit? I'd consider fitting
Panaracer Paselas in a 1 1/8" width if it's reasonable, but
I don't want to get the guy into trouble.

BTW, I doubt I can get him to spend for a new wheel set.
And his Dia-Compe "G" single pivot side pull brakes are at
the limit of their 60mm drop, so moving to 700c wheels would
require new brakes, or at least some antique drop bolts.

Again, in summary: Are 1 1/8" tires on 12.5mm rims likely to
work? How risky is that?


Other Trek models then, and many other bikes, came with Rigida 1319 or
1320 and 27 x 1-1/8 tires stock. It's not only theoretically OK, it was
a once-popular combination in huge volumes. Not to worry.


Good news. Thanks, Andrew.


--
- Frank Krygowski
  #6  
Old September 11th 16, 03:42 AM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,945
Default Wide tire on narrow rim?

On Fri, 09 Sep 2016 16:56:27 -0500, AMuzi wrote:

Other Trek models then, and many other bikes, came with
Rigida 1319 or 1320 and 27 x 1-1/8 tires stock.


Ah, the first wheels I ever built- 1977- were the low end Avocet hubs
laced to those Rigida rims. Rode those for years; still have the hubs
in the original tattered box.
  #7  
Old September 11th 16, 04:16 AM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 5,870
Default Wide tire on narrow rim?

On Saturday, September 10, 2016 at 7:42:57 PM UTC-7, Tim McNamara wrote:
On Fri, 09 Sep 2016 16:56:27 -0500, AMuzi wrote:

Other Trek models then, and many other bikes, came with
Rigida 1319 or 1320 and 27 x 1-1/8 tires stock.


Ah, the first wheels I ever built- 1977- were the low end Avocet hubs
laced to those Rigida rims. Rode those for years; still have the hubs
in the original tattered box.


Those were, IIRC, Ofmega hubs.

PAB and Avocet had all sorts of odd-ball stuff -- the thinned down triple crank and the two bolt seat-post (mine broke). I also broke an Ofmega track crank that I bought off a sale table at PAB. I remember that, right on the corner of Big Basis and Saratoga -- sort of SMS stomping grounds. It was a long ride home using one leg.

That was a fascinating era with all the not-Campagnolo brands before Shimano convincingly snatched the market.

-- Jay Beattie.
  #8  
Old September 13th 16, 03:33 AM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,945
Default Wide tire on narrow rim?

On Sat, 10 Sep 2016 20:16:47 -0700 (PDT), jbeattie
wrote:
On Saturday, September 10, 2016 at 7:42:57 PM UTC-7, Tim McNamara
wrote:
On Fri, 09 Sep 2016 16:56:27 -0500, AMuzi
wrote:

Other Trek models then, and many other bikes, came with Rigida 1319
or 1320 and 27 x 1-1/8 tires stock.


Ah, the first wheels I ever built- 1977- were the low end Avocet hubs
laced to those Rigida rims. Rode those for years; still have the
hubs in the original tattered box.


Those were, IIRC, Ofmega hubs.


I think that is correct, just rebranded. They were basically Campy
clones, although the cones matched Campy NR track cones rather than roa
cones. At least IIRC from replacing them once about 20 years ago.

PAB and Avocet had all sorts of odd-ball stuff -- the thinned down
triple crank and the two bolt seat-post (mine broke). I also broke an
Ofmega track crank that I bought off a sale table at PAB. I remember
that, right on the corner of Big Basis and Saratoga -- sort of SMS
stomping grounds. It was a long ride home using one leg.

That was a fascinating era with all the not-Campagnolo brands before
Shimano convincingly snatched the market.


There was a lot of interesting- if not necessarily well designed or
executed- stuff in the mid-late 70s. Weyless hubs and other components,
Hi-E, Bullseye hubs/BBs/jockey wheels, etc. The one that seems to have
stuck around is Phil Wood. Then Sun Tour made a pretty good challenge
to be the main team, but Shimano came back and ate their lunch.
 




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