General Discussion Triathlon Talk » Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires? Rss Feed  
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2015-06-22 6:58 PM


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Subject: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
Hi,

I'm looking for feedback about where to best put my money in a tire upgrade, if at all. Currently I have my brother's 2001 Fuji Aloha TT with 650c x 20mm tires, and they go flat quite often. The tires say 130psi minimum and 165 max. I can't ride like this with the constant flats. I know the current thinking is to go with wider tires, and 650c tires max out at 23mm width.

However my 700c road bike already has 23mm tires... and I've been wondering what's my best choice... do nothing and just use my road bike @ 23mm? Change my road tires to 25mm or 28mm? Or put 23mm on the Aloha? Which tire change would give the most improvement? And would the improvement be worth spending the money on?

I'm not especially competitive, I simply like to finish, but I'm working on upping my distances from sprint to Oly, and hopefully half IM next year, so a meaningful reduction in effort and overall time would be nice, but a 2 minute gain would not be worth it unless there was some side benefit like much greater comfort and better legs for the run. BTW I train in the Chicago area so roads are hit-or-miss especially with frost damage. TIA!!


2015-06-23 6:30 AM
in reply to: motri88

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
The missing data is your height and weight If you are shorter than 5'2" you might get a better fit with a 650 wheel. 20mm tires are best for riders weighing les than 120lbs. 130 PSI is extreme considering HED recommends 90 PSI on its wider rims.700c wheels have a theoretical advantage over 650cc wheels. Everything points to your road bike being a better strategy. Add clip-on bars for aero position and you should do well.
2015-06-23 7:34 AM
in reply to: motri88

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Champion
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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?

I know J&B Importers (supplier to a lot of bike shops at least in this area) have 650cx25 tires listed in their selection, and if you go to some Euro suppliers you may find more selections. However, "constant flats" says something else to me than tire size -- like there's something stuck inthe tire that you're not getting out, or the rim strip is moved or torn at a spoke hole, or there's a bur at the valve hole... something is causing the flats other than the tire, I'm thinking.

2015-06-23 7:35 AM
in reply to: Six000MileYear

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Champion
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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?

Originally posted by Six000MileYear .700c wheels have a theoretical advantage over 650cc wheels.

What, exactly, is this theoretical advantage?

2015-06-23 9:23 AM
in reply to: motri88

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
What does the rim tape look like... repeat flats can be a tire issue or a rim tape problem as well. Get velox to replace the rim tape.
2015-06-23 9:26 AM
in reply to: briderdt

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
Originally posted by briderdt

I know J&B Importers (supplier to a lot of bike shops at least in this area) have 650cx25 tires listed in their selection, and if you go to some Euro suppliers you may find more selections. However, "constant flats" says something else to me than tire size -- like there's something stuck inthe tire that you're not getting out, or the rim strip is moved or torn at a spoke hole, or there's a bur at the valve hole... something is causing the flats other than the tire, I'm thinking.




More often then not rim tape / strip is the issue. Pull both tires off pull the rim tape off and inspect visually and run your fingers looking for sharp spots.


2015-06-23 10:48 AM
in reply to: Six000MileYear


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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
I'm 5'9" and 168lbs. The reason the TT bike has 650c wheels is because that was the fad when my brother bought the bike, this was before most tri bikes were really being designed to fit 700c wheels. I considered aero bars for the road bike but the drops are carbon so I don't want to risk breaking them. Thanks.
2015-06-23 10:56 AM
in reply to: simpsonbo


11

Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
I have already replaced the rim tape on my road bike, so I did consider that early on. I inspected the rim tape and the inside of the tire and it seemed clean and flat to me, and last year a bike shop checked my rear wheel after a flat and they thought it was good. And the tires themselves are Kevlar so they should be keeping debris out. And they're not popping at the valve hole or the rim tape area.

My guess is that the pressure is too high for "road" riding, and going to a larger size will mean I can ride at less psi and hopefully not go flat so often. Since 650c tires seem much more expensive than 700c, my question is whether I'll see enough improvement to justify spending $100 on new 650c tires, or just stick with my road bike... and if I stick with my road bike should I maybe spend $30-$40 on wider road bike tires... Thanks.
2015-06-23 11:00 AM
in reply to: briderdt


11

Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
The 700c advantage I've read about is lower rolling resistance. This definitely interests me. Actually last night I took a first ride on a 30 year old Fuji steel bike I found cheap, 27 x 1.25" tires, and it took more effort to ride but wasn't nearly as slow as I thought it would be. I could imagine the lesser rolling resistance was part of that.
2015-06-23 11:21 AM
in reply to: briderdt


11

Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
I'll check with J&B, I found their website. I'll do a really thorough check of the rims and tape, although the punctures weren't in those spots. I'm really thinking it was the super high pressure.

Also I forgot to mention in my first post that my tubes, even my replacement tubes, were pretty old.
2015-06-23 1:18 PM
in reply to: motri88

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?

Originally posted by motri88 I'm 5'9" and 168lbs. The reason the TT bike has 650c wheels is because that was the fad when my brother bought the bike, this was before most tri bikes were really being designed to fit 700c wheels. I considered aero bars for the road bike but the drops are carbon so I don't want to risk breaking them. Thanks.

It really depends a lot on your preferred position. The steeper you prefer your effective seat tube angle (regardless of how the frame is designed), the more the 650's make sense. I'm 5'10", ride a 54cm road frame with 700c's, but my tri bike is 650 and I prefer it that way.

[caution -- bike frame design talk follows]

My effective seat tube angle is around 82 degrees (I go pretty darn low up front, and maintain the same hip angle as on my roadie), which puts my weight WAY forward. In order to maintain good handling, I have to stretch that front-center way out, and bring the rear wheel as close under me as possible. 700's run out of room right quick. Most production frames are built around a 76-78 degree seat tube angle. Not that far out of the realm of road bike designs. QR was one of the first to get it right, way back, but even now (with Dan Empfield no longer at the helm), they've gone more mainstream and backed off. Too bad, in my opinion.

So while it may be considered a "fad" by some, I see it as smart design solution. I've heard way too much bike-shop drivel about how 650c's are not as good, and it comes down to erroneous folklore and not wanting to stock more tire and tube sizes (though why it's all okay for MTB's now, I'll never know). I've had to bite my tongue too many times in shops (especially when I worked at one) and not completely undermine the salesman (and the shop owner) when they're steering some one away from the smaller wheels.



2015-06-23 1:37 PM
in reply to: 0

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?

Originally posted by motri88 The 700c advantage I've read about is lower rolling resistance. This definitely interests me. Actually last night I took a first ride on a 30 year old Fuji steel bike I found cheap, 27 x 1.25" tires, and it took more effort to ride but wasn't nearly as slow as I thought it would be. I could imagine the lesser rolling resistance was part of that.

Yep, and I've got a gravel bike with 700x35 Sammy Slick's (not slick, by any means) that I run at 60psi rear / 50psi front, and when I'm "on it", for the same course under similar conditions my average speed is less than 1mph slower than riding the road bike with 700x23's at 100/90. It ain't rolling resistance that's the problem.

For "every day" spoked wheels, the 650's actually have an advantage of a more extreme spoke angle (the spokes get to centerline sooner), they produce less resistance. For race wheels, it's basically a push. Smaller wheel would generally mean less wind resistance anyway, but for a given frame size you trade it for tube length, so it's a push again. So, aerodynamically, there's no appreciable difference.

The lower moment of inertia means they spin up faster (I chose 650's for my track bike for this very reason). They also spin down faster, but you shouldn't be coasting in a tri anyway, right?

Gearing wise, just add 2-3 teeth to the chainring for equivalent gearing. A standard 53/39 on 650's is about the same as a compact 50/36 on 700's. So overall, lighter.

The real pay off of the 650's comes in the frame geometry and the body position it can allow. This is the basis for the oft-quoted "people of X height or Y frame size will benefit, but above that you're better off with 700's". My response to that is "it depends". Meaning it may be true, but not always (and not even most of the time, from my experience).

Anyway... I'll get off my soap box now. I could go on and on (too late, eh?).



Edited by briderdt 2015-06-23 1:55 PM
2015-06-23 10:29 PM
in reply to: 0

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Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
I'm 5'9" and 175 lbs.
My favorite tire configuration is 23mm front / 25mm rear at 95 PSI. It's a slightly faster and more comfortable ride than a pair of 23mm at 100 PSI.
Some tri bikes may not have the clearance for 25mm tires.

Edited by Six000MileYear 2015-06-23 10:43 PM
2015-06-26 4:56 PM
in reply to: Six000MileYear


11

Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
OK well I ordered 25mm tires and tubes. Probably I'll have to deflate them to get them past the brake pads. Thanks everyone for the advice!
2015-07-07 4:00 PM
in reply to: motri88


11

Subject: RE: Upgrade my 650c x 20 TT tires or my 700c x 23 road bike tires?
Originally posted by motri88

OK well I ordered 25mm tires and tubes. Probably I'll have to deflate them to get them past the brake pads. Thanks everyone for the advice!


I did my first ride on the new tires, back and forth on a fairly flat and straight stretch of ashpalt trail for 25mi. Much more comfortable than my old tires. I now have to decide on whether to have a pro fitting done on this bike, and whether to buy more tires as spares... I don't think these will be available much longer.
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