Bicycle Mechanics - 730 Trek Hybrid and want more speed...
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Here's the specs: I have a '97 Trek 730 Hybrid. 3 front rings...24-34-42. 7 speed cassette...11-13-15-18-21-24-30. Sram SRT 4.0 handlebar twist type shifters. Shimano Acer X Front DR, bottom pull.
I want to try to make whatever changes I can to achieve more speed. I'd like more top end speed and was wondering if changing front rings and/or rear cassette would help achieve this. Looking at the rear cassettes you can tell I'm always in the smallest cogs. A more experienced rider noticed the wear pattern and said I should be in the middle to upper cogs more but with the gearing I have it would be hard to do.
So, my question....from a real newbie when it comes to specs and the mechanics involved...how hard would it be to make the needed changes and what changes would you make (rings, cassette, DR, etc)?
Is this something better left to the LBS?
Thanks for your insight.
IF you dont already have them, slicks would be a BIG improvement (assuming you are riding on pavement)
04-27-06, 03:17 PM
If you are going to ride this on the road, try a 48-38-28 crankset(35.00)at your LBS. If you have MTB
tires go to the narrow high pressure slick that will fit the rim. If you have 700x35 or 38's change to high pressure 28's
+1 on the tires. I changed from 38mm Specialized tires to Michelin Transworld City 32mm. The latter seem to be a "slim" 32mm. The bike feels a lot faster and my average commute times have come down after the change.
04-27-06, 08:20 PM
You don't mention why you can't go faster. Is it because you are spinning out and have reached your maximum cadence, or is it because you just can't push any harder?
The former can be improved with a gear change, the latter by changing to slicks and/or improving your fitness or riding technique.
As to gear changes.... you have an 11 tooth cog on your cassette so that can not be improved. Your FD has a 22 tooth limit so the largest chainring you could fit would be 46, if you want to keep your current lowest gear (and 24t small chainring). This is a simple and cheap change and only requires unbolting the big chainring and bolting on a new larger chainring. It would give you about 10% more speed for a given cadence.
That's what I'm looking for. As it is now I'm in the big ring in front and pedaling like hell in the smaller cogs. I have a road bike with bigger front rings and can get plenty of speed using the big ring and staying in the middle on the back cogs. I run marathons and have plenty of endurance so I don't think it's a fitness thing. I like to maintain a cadence of around 90 as that seems to be about right for me. I'd just like to maximaize that cadence. Like I said, I'm new to this mechanics stuff and really have no idea if changing rings and gears is the answer.
04-27-06, 09:12 PM
You can't get any smaller than an 11T cog so your only approach is larger chainrings. If you have an MTB crank your choices are limited but any road crank will give you as large a ring you want.
04-27-06, 09:17 PM
OK it sounds like a new chainring is the go...
You need to find out what bolt size/pattern your existing chainring has, i.e. four or five bolts and what is the Bolt Centre Diameter (BCD). Once you have this info, either go down to your lbs and ask for a 46t chainring with that bolt pattern. Or search the net.
There is a special tool for holding the back of the chainring bolts, it only costs a few bucks, but you may be able to manage without.
Finally, the 22 tooth limit of the Shimano triple front derailleurs is really only a guide, you may be able to go a little larger, possibly a 48t, but this is just a matter of trial and error. Also, the bigger you go the longer the chain will need to be, I would guess that going to a 46t won't be a problem with your existing chain, but it may be. Chains aren't all that expensive.
A good source of info is always www.sheldonbrown.com
04-27-06, 11:13 PM
Your wind might be great, but you use different muscles for the bike than for running. How do your legs feel after a long haul up a hill?
I also have a 730, but a newer model. The change to higher pressure tires is a very appealing idea.
04-28-06, 05:29 AM
Higher pressure narrower 28mm tyres.
Pedal attachment system, either toe clips of cliples pedals.
A road triple (28/38/48) or compact double (34/48) chainset
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