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Old 07-06-10, 01:12 PM   #1
Lobs616
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Width of tires for trail riding on a Sirrus

I am looking to buy a used bike to get back into riding. I just found some great trails near my house that are hard packed stone dust. I would also like to be able to do some riding on roads also. Therefore decided to look for a hybrid. Found a great deal on a 2003 Specialized Sirrus. Evidently, the owner just replaced the tires with 700 x 25 tires for a road ride last month. Will these tires work ok on the trails or will I need to replace with something wider. If I need to replace, what would you suggest for this purpose and what will fit on the Sirrus?
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Old 07-06-10, 04:41 PM   #2
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Any tyre wider than 23 will fit and even a 23 may, so you have plenty of choice there.
For doing both fast road and offroad you should be looking for "cyclocross" tyres, which are specificaly designed for this purpose.
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Old 07-06-10, 05:46 PM   #3
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For a mix of road and trails like you describe I think you would prefer to be in the 28 - 38 mm range. You could even go wider if the rims are wide enough, for road use it is not the width so much as the tread that becomes a "problem". Knobby treads add more rolling resistance than width does on a road and some find the noise and handling objectionable too but a wide, smooth tire can be quite fast and pleasant to ride. A trail like you describe is fine with 28 mm tires if it is hard packed. A 28 mm tire will handle some fair degree of softness and gravel even for at least short distances, I've not tried long distance riding on such surfaces and 28 mm tires. I have done a loop of about a mile on 28's on a mix of turf, packed dry dirt, moist slightly soft dirt, pine needles, and a fairly steep gravel up grade and the 28's were not an issue for steering, traction, or control. If the surface will get quite soft in places or during some seasons a wider and knobby tire might be called for. Are horses allowed on your trails? The bike path near me is packed limestone on its far north end and the 32 mm tires I currently have are great with it except that it is all cut up by horse hooves. It is literally like riding on cobblestones. I don't ride that section often and not very far yet. It may be that lowering the pressure in my 32's will make it more bearable, but if you will be dealing with a lot of surfaces like that you might want to go up to 38 mm. On the other hand if your packed trails are flat and smooth the 25's will probably do for now and you can just go wider when you wear them out. There is no harm in trying them for a while to see how they work.

Ken

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Old 07-06-10, 05:57 PM   #4
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I think 32c tires would be a good compromise between fast rolling, and bump absorbing for packed stone trails. 35c wouldnt be bad, either. Something like the Schwable Marathon Supreme would have enough tread for the stone, but smooth enough for road, as well.

I use the stock 28c tires and only ride road, I am thinking of 25c sometime, but not till these tires wear out or become problematic.
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Old 07-07-10, 08:19 AM   #5
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I would suggest that you try 'em out. If your aglime is like ours, it's like riding on concrete when it's dry, and not much good for riding with any tires, if it's soaked.

You might be very surprised, when you find out they are fine. 25mm is almost an inch wide, and we rode on 27X1" on those things for many years. In any case, 28s or 32s should be more than sufficient. And, you will probably find out you don't need anything but slicks, which will even help you on the road.

How wide of a tire will that Sirrus take?
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Old 07-07-10, 03:04 PM   #6
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I would suggest that you try 'em out. If your aglime is like ours, it's like riding on concrete when it's dry, and not much good for riding with any tires, if it's soaked.

You might be very surprised, when you find out they are fine. 25mm is almost an inch wide, and we rode on 27X1" on those things for many years. In any case, 28s or 32s should be more than sufficient. And, you will probably find out you don't need anything but slicks, which will even help you on the road.

How wide of a tire will that Sirrus take?

With or without fenders??
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Old 07-07-10, 03:10 PM   #7
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I too prefer 32mm as an all-purpose tire. But not all 32mm's are the same. I've measured different tires all claiming to be 32mm and found them to range from 29mm to 34mm.

A friend of mine puts in hundreds of miles on dirt & limestoned trails on 28's.

You can certainly do it on 25's, but I find the ride harsher than I like it. Particularly if you use an armored tire. The Specialized Armadillos are quite hard, IMHO.

A 32mm running at 80 to 90 psi is nice on a dirt trail.
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Old 07-07-10, 03:23 PM   #8
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Tire makers vary a lot on there measurements, My Kendra 38c, with calipers only come out to 34c...and for me
I could not see going any smaller, if you seen the( Down Hill Gravel Road Video) , those are some pretty
large rocks, and mine barely are wide enough....now if I did not ride such roads, I would like to go narrower,
If your just riding hard packed trails, I think you would be fine, and faster...but when you add sand and rocks,
you have to go wider....Richard
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Old 07-07-10, 03:27 PM   #9
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It really all depends where you ride..

Tire makers vary a lot on there measurements, My Kendra 38c, with calipers only come out to 34c...and for me
I could not see going any smaller, if you seen the( Down Hill Gravel Road Video) , those are some pretty
large rocks, and mine barely are wide enough....now if I did not ride such roads, I would like to go narrower,
If your just riding hard packed trails, I think you would be fine, and faster...but when you add sand and rocks,
you have to go wider.... Richard
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Old 07-07-10, 03:44 PM   #10
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I'm a big fan of fenders, as they keep me and the bike (including the drivetrain) so much cleaner - and so much better lubricated.

Soooo - enter that into the equation.

How much room do you have in there for tires, and fenders - in my case Planet Bike Hardcore Hybrid Fenders, at 43mm internal width, a few more mm wide externally ( I can measure them if you want me to) cover a 40mm wide tire barely adequately, and are perfect for 32-35mm wide tires.

Plus, they keep the goose poop off my water bottles, and out of my pump innards.
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Old 07-07-10, 03:46 PM   #11
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There are a few Sirrus riders on this sig, who will chime in with tire sizes and fender sizes, as well. They are already running fenders, and have tried various tire sizes.
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Old 07-07-10, 03:56 PM   #12
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Just as a point of information, on 18mm internal width rims, at 92 PSI, my Schwalbe Marathon Supremes, measure 36mm wide on a 622-37, 700CX35, and 40mm wide on a 622-42 , 700CX40. Actual measurements. Like I say, the 35s fit that fender perfectly, and the 40s adequately.
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Old 07-07-10, 04:04 PM   #13
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Another consideration - I love the combination of a 40 on the rear, with a 35 on the front of my Crosstrail - not knowing what the Sirrus will accomodate. I wouldn't be afraid to try a 32 on the front, either; but, the 35 on the rear made my bike ride much more harsh - the 35 on the front, didn't affect the ride, but sure helped the handling

The 40 on the rear helps the ride comfort, and the 35 on the front helps the steering and handling. You may be happy with a combination, as well.
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Old 07-07-10, 05:47 PM   #14
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Quote:
Originally Posted by AdelaaR View Post
Any tyre wider than 23 will fit and even a 23 may, so you have plenty of choice there.
For doing both fast road and offroad you should be looking for "cyclocross" tyres, which are specificaly designed for this purpose.
Cyclocross tyres are designed for a variety of conditions, just like MTB tyres. Some are for mud, some are for hardpack, some are for gravel. And they tend to be 35mm, which is too wide to fit on most models of the Sirrus - its narrow tyre clearance makes it a poor choice as off roader.
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Old 07-07-10, 05:52 PM   #15
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Anyway. If the bike can fit them - which it probably can't - then the state of the art in dual purpose tyres are the Schwalbe Dureme and Extreme. The first is faster on the road, the second goes further off road. They use the same technology as the Supreme that has already been mentioned but with a more agressive tread pattern that gives better braking and cornering off road. See

http://www.bikeforums.net/showthread...res.-(meanwile!)
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Old 07-07-10, 07:04 PM   #16
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If I'm not mistaken, don't some of the Sirrus models come with 32mm wide tires, as OEM????

How much spare room is in there?
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Old 07-08-10, 05:34 AM   #17
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If I'm not mistaken, don't some of the Sirrus models come with 32mm wide tires, as OEM????
1. There have been so many damn models of the Sirrus over the years

2. What one maker calls a 32 can often be a 34 or 30. Plus this measurement won't include protruding teeth. So this gets messy.

The OP's best bet is probably to try fitting 35mm Duremes. (If he is willing to pay the price. Otherwise for "hardpacked dust" he could try cheap but sticky 35mm slicks.) Hopefully they'll fit and they're a tolerable width for light off roading as long as the rider isn't too heavy. Fortunately hardpacked dust is an easy ride as long as there isn't bad rutting.

Even for a heavy rider 35mm is ok as long you're willing to put up with being banged about and steer around or directly over every tree root, hard rut, and small branch. I'm 220lbs and my crosser has 35mm tyres on, I spend a *lot* of time off the seat using my arms as suspension. I can ride light MTB trails and do it fast, but riding them on 35mm requires total concentration - taking a small root or rut at the wrong angle can mean a wipeout.

The difference between 35mm and 40mm doesn't sound much but the volume of air in a tyre is proportional to the square of these sizes - so a 40mm has about 50% more. That gives you MUCH more suspension. Oh - and the reduced traction of a 35mm makes cornering and braking much "interesting" too.

Measure the bike for tyre clearance with a ruler - the chainstays are usually the problem. And then order. If the tyres you order won't fit, then just send them back - a decent store should be cooperative. And measure the side of your rims and check they'll take 35mm tyres with the chart here:

http://www.sheldonbrown.com/tire_sizing.html

- There shouldn't be a problem with this, but it's smart to check.
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Old 07-08-10, 07:51 AM   #18
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I do not care for 28's on packed limestone. Bigger is better there IMHO.
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Old 07-08-10, 12:09 PM   #19
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Wow, what a thoughtful group you all are. There is a lot to consider here. Of course as I am getting closer to pulling the trigger on this I have started to re-think my decision altogether. I love the Sirrus and hope to be cycling on the road again someday but for right now I think I will spend most of my time on the trails. The trails are definitely hardpacked dust and gravel which is hard in most places, no tree roots or branches but there are some areas that are rocky and some areas that have loose gravel in them as well as a few spots where most of the surface has washed off and it is now hardpacked dirt. So, now my question is do I get the Sirrus and swap out the tires (according to BP the stock tires were 38 but not sure if that is accurate) to 32 or 35s or should I be looking at a different bike altogether. Maybe I should even get a cheap mountain bike for now until I am comforable getting out on the roads. The area around my house is very hilly and I am in pretty bad physical shape right now so the flatness of the trails is making my transition back into this sport much easier. Sorry for changing the direction of this thread but I am looking forward to your responses.
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Old 07-08-10, 12:28 PM   #20
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I don't think you will find 38s on there - more likely 32s or 28s. 32s will be fine, and you will probably appreciate the lighness of the Sirrus, over a bike that has suspension parts. It will be more nimble.

If it turns out that you really "NEED" tires with more biting surfaces, your next set could be a set of cross tires - my guess is that you will prefer the quickness of a more slick road tires. Packed earth is just like riding on pavement, and loose gravel will give even the knobbies fits. Just learn to "float" em thru the loose stuff, by letting them find their own way across, while you hold the bars loosely.

Keep in mind, that the Sirrus is a pretty Performance oriented Hybrid, and it will do passably well on the road, while still giving you good visibility and control.

I'm crap keeping names straight, but Mike Shoup and Ryan (Nytmber) both did a very nice job of fitting fenders on their Sirrus', though you might have to buy a different front derailleur to gain a little room - that's no big deal, they are cheap.

Enjoy the bike - and put lots of miles on it...... and keep in touch, with your impressions of it.

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Old 07-08-10, 01:34 PM   #21
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I don't think you will find 38s on there - more likely 32s or 28s. 32s will be fine,
Yes, I certainly couldn't have put 38s on my Sirrus. 32s will be a LOT better than 28s - but nearly as good as 35s. How wide a tyre is absolutely necessary depends partly on whether there a trail obstacles like stones and hard ruts, and partly on the weight of the rider. Setting your tyre pressure right is just as important as getting tyre choice right. These links should help, especially the second:

http://www.rivbike.com/article/components/tires

www.rivbike.com/article/components/pick_a_tire_chart

Quote:
you will probably appreciate the lighness of the Sirrus, over a bike that has suspension parts. It will be more nimble.
Cheap suspension is a bad joke. And suspension on a hybrid is a worse one. When a hybrid's tyres can't handle the conditions you are riding in, that's a sign you need a real MTB with room for wide rubber, a stronger frame and rims, and a geometry that is balanced for riding off road.

Oh - and if the dust really is hard packed then avoid off road tyres with aggressive triangular teeth on the cornering surfaces. These are great for cornering on mud, where the teeth dig in nicely. But if you corner aggressively on a hard surface then the teeth will bend and so the can tyres slide out from under you. This is not nice!

An online friend just tested out those Duremes on hardpack with amazing results, if you don't like or can't fit them then google "hardpack tire 700c".

Re bike choice - a rigid (ie no suspension) 29er could be a good one. Google the phrase and ask for tips on deals on entry level 29ers on the MTB forum. These are the most versatile flat bikes around, tougher than a normal hybrid (they are just a beefed up hybrid really) but fast enough to hang on to a racing bike if they can get in its slipstream:

http://pfunwithpflug.blogspot.com/20...unon-road.html

Otoh, a standard 26 inch wheel MTB is a very versatile bike too and they are easy to find used.

If you've not bought the Sirrus yet, then I wouldn't. Depending on the model they can be part carbon and part aluminium, and mixed material bikes are more likely to suffer frame failures. Most of all, the Sirrus is just not designed for riding off road. The sharp frame angles and high main tube make it one of the last bikes I'd want to be on if the front tyre hit a rock at speed, or the back tyre slid on gravel. That doesn't mean that it is a death trap - you'd just have to ride a little slower and more carefully - but it is the wrong tool for the job.
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