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  1. #1
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    Switching to smaller tires?

    I'm currently 295 pounds and this summer have been riding a Specialized Crosstrail. It still has 100% stock components and in most respects I love the bike, but it feels sluggish. I can pretty much ride it on roads all day, but only at like 14 mph. I can get it up to 22 but with a level of exertion that I can't keep up for very long. Since I otherwise love the bike and would just like to speed it up a bit (I'd like my "distance" speed to be more like 18) I've been thinking of trying it with smaller, smoother tires.

    The tires on the bike right now are 700x38 with a knobbly tread (specialized trigger sport). Rough terrain is no problem at all; they're not great on sand or mud but anything short of that almost isn't even noticeable. I have had no flats. I inflate them to 100psi and seem to lose 5-10 on a typical ride. They really seem pretty bulletproof.

    Thing is, even though it's great on rough terrain I am on pavement most of the time. So I was thinking of putting a 32 or 28 city tire on it. The questions are, is this advisable at my weight, and would it make any appreciable difference? Or is the answer just to get in better shape or get a road bike? I've test ridden a few road bikes and I am just not crazy about drop handlebars.

  2. #2
    Still learning oddjob2's Avatar
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    I suggest trying some 28s. Panaracer Pasela TourGuards.
    Life is like riding a bicycle. To keep your balance you must keep moving. Albert Einstein
    2014 Additions: 1985 Trek 560, 1992 Trek Multitrack 700 (my 2nd), 1994 Trek Carbon 2200, Peugeot PX-10, 1981 Schwinn Voyager, 1989 Bridgestone RB-1

  3. #3
    Ancient Clydesdale 2 wheeler's Avatar
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    Tires make a huge difference. Knobbies waste a lot of power and you would go faster on slicks.

    Tires are one thing, but when you increase speed, the biggest loss of power goes to aerodynamic drag. The Crosstrail puts your body nearly straight up and this makes for a lot of drag. A drop bar bike would allow you to go faster for several reasons, but primarily because of the improved aerodynamics.

    The tires would be a cheap experiment to see how much speed you would gain. Improving aerodynamics is a bit more complicated and potentially more expensive. For your weight, it could be a good idea to stay on the bike you've got until you lose enough to try a road bike.

  4. #4
    Big Boned Biker IAMAMRA's Avatar
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    I just switched to 28's from 32's and weigh about the same as you do. I didn't notice much for speed, but the handling was very noticeable to me. Turns much sharper now, and doesn't "hug" the road as much.
    www.BigBonedBiker.Wordpress.com

  5. #5
    just pedal donalson's Avatar
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    as mentioned knobby tires waste power... so simply going to a smooth center tire will help things out...

    going to a smaller tire does have some other issues... the smaller the tire the higher pressure is needed for ideal drop http://www.dorkypantsr.us/bike-tire-...alculator.html

    at your weight + your bike out back you are looking at about 115psi if you went to a 32c tire but 145psi with a 28c... if you wanted a 23c you're looking at over 200psi...

    I'm slightly heavier then you and am running Panaracer Pasela 32c tires they run nicely at about 110 psi its prob worth spending a bit more for the TourGuard version as mentioned above for the extra flat protection...

    that being said going with a 38c tire with a smooth tread in center will help out a lot on the road... I rand some kenda kross tires in both 42 and 38c happily on a bike that mostly saw the road but occasional gravel road/greenway
    mtbr clyd moderator

  6. #6
    Nigel nfmisso's Avatar
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    tread or lack there of is far more important than width.
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  7. #7
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    I just switched from 35's to 32 and I gained about 2mph. As was mentioned earlier, the handling is very different and much quicker steering. I prefer the new ones. I don't think I'll go any narrower but I'm quite happy at 32. It's a cheap change.

  8. #8
    Texas Tornado copswithguns's Avatar
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    I'm ~300 and I ride on 25s. YMMV. I would go with others and say drop to 28s at least. I'm a fan of 25s though; Some don't like the "rough" ride on them but man do I fly down the road on those.
    "Speed never killed anyone. Suddenly becoming stationary...Now that's what gets you." -Jeremy Clarkson

  9. #9
    Senior Member mkadam68's Avatar
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    Quote Originally Posted by donalson View Post
    going to a smaller tire does have some other issues... the smaller the tire the higher pressure is needed for ideal drop http://www.dorkypantsr.us/bike-tire-...alculator.html

    at your weight + your bike out back you are looking at about 115psi if you went to a 32c tire but 145psi with a 28c... if you wanted a 23c you're looking at over 200psi...
    Don't use that stupid calculator. Anything above around 130 and your back tire will start bouncing unless you're riding track. OP: keep 'em about 115--120psi, you'll be fine.

    Visit The C-Blog : the blog about cycling.

  10. #10
    Getting older and slower!
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    Quote Originally Posted by mkadam68 View Post
    Don't use that stupid calculator. Anything above around 130 and your back tire will start bouncing unless you're riding track. OP: keep 'em about 115--120psi, you'll be fine.

    +1

    Those calculations are way off. I air my tires to the max the tire recommends to about 10psi over. Never had a pinch flat in my 30+ years of serious cycling. Weight during that period ranged from 185 to 335, but mostly in the 210 to 220 range.

    And yes, 28 or 32 non-knobby tires would be better for the road and even crushed rock bike paths (like a lot of rails-to-trails). Knobby tires are for off road stuff.
    Last edited by Cychologist; 09-21-13 at 08:42 AM.

  11. #11
    Senior Member Bill Kapaun's Avatar
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    Although I'm a fan of skinnier tires (230ish & ride 26mm) I think being around 300 lbs, you'd be better off with the 32's.
    Less than that and you have to run excessively high pressure which makes the tire too hard. Road "buzz" numbs the hands and you really don't have any "squish" if you hit a pot hole etc.
    If you get down to 260, reward yourself with 28's.

  12. #12
    Senior Member Blue Belly's Avatar
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    I built my cyclocross bike up with 34mm tires. I moved down to 32mm tires & it made all the difference in the world. Same tire, different size. There's a lot of variance in tread patterns, especially in cross tires. I have a pattern that is designed for offroad yet, rolls pretty well on pavement. A smooth tire will obviously roll a little better. I like the 32's, I ride a a lot smaller tire on my road bike. The 32's aren't the fastest. They don't feel sluggish, though.

  13. #13
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    Quote Originally Posted by Bill Kapaun View Post
    Although I'm a fan of skinnier tires (230ish & ride 26mm) I think being around 300 lbs, you'd be better off with the 32's.
    Less than that and you have to run excessively high pressure which makes the tire too hard. Road "buzz" numbs the hands and you really don't have any "squish" if you hit a pot hole etc.
    If you get down to 260, reward yourself with 28's.
    I like this idea. My LBS (which I went by this morning and turns out to have a pretty poor selection of tires in the 28-32 range in stock) was of the opinion that the rims on my bike would be fine with 32s and would probably be okay with 28s but that that would be pushing it a bit. The last time I hit a weight loss milestone I bought a bike, so that is a system that works.

  14. #14
    just pedal donalson's Avatar
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    For your rims fitting the tire... it shouldnt be a prob... ive got one of the wider 29er rims on mine and run 32c no prob and could go 28c... I wouldnt go narrower though
    mtbr clyd moderator

  15. #15
    Senior Member jc650's Avatar
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    That calculator thing seems ridiculous to me to. I bought my road bike with 25's last year at just over 300 lbs. I initially suffered some flats because I didn't realize you had to keep them inflated that high. I bought higher quality tires kept them around 125 and haven't had any problems. I also have a 29'er mountain bike that I decided to take the 2" wide off road tires off and put on Michelin city 47's instead and to be honest on the blacktop I only gained around 1mph on most of my rides. Take a look at those Michelins they are pretty tough tires and roll nice and they are not to expensive. They certainly make less noise but my average went from 15 to 16 not 15 to 17 or 18 like I expected. What helped me most was losing over 50 lbs in the last 4 months not smoother tires.

  16. #16
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    As an update my bike now has Schwalbe Marathon 32s on it, and I don't think there will be any trouble with my weight, the ride still feels really solid.

    Speed-wise my top speed is up marginally (~1 mph) but my average speed is up significantly (~4 mph). I'm not entirely sure why this is but riding in high gear on a flat definitely isn't as tiring as it was before. The bike is also sharper in the corners now which I quite like actually.

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