1.25" slicks safe on a MTB?

P

pizark

10 W
Joined
Jun 16, 2008
Messages
66
Hi ya'll,

I was at Performance Bike a few days ago and saw these 1.25" MTB slicks on clearance for 8 dollars each.

I'm riding a Trek 4300D with the stock knobbies right now with a Crystalyte 408 rear hub. The Crystalyte kit came with a topeak bag & rack combo that holds 4 (12v10ah) SLA batteries). I think each battery is about 7 lbs. Funny, I didnt think 28lbs was that much weight till I put the bag on the rear rack.... boy was I wrong. So 28lbs, weight of the motor, controller, and all that other junk makes the back end heavy. I'm 5'10 @ 175lbs, also.

My question is,... what are the benefits and drawbacks of putting these new slicks on?

My trek is an aluminum hardtail,.... am I gonna dent a rim, or worse by mounting these? The rear wheel looks pretty darn tough with the fat rim and spokes.. but i dunno, that's still a lot of weight. I ride mostly on the street, but i'll occasionally switch onto the sidewalks and vice versa. Even with my stock tires,... i was hesitant do push any sort of real speed on sidewalk type surfaces (bumps, indents, etc.). The slicks were 8 bucks each, should i gamble?

Some guy at some other bike shop said that the additional protection a 2 inch tire would provide my wheel vs a 1.25 would be marginal, at best. Is that true?

Appreciate any advice u could give me.

Paul
 
Your wheel would probably be fine. Maybe a few more loose spokes. Then again I run a 23c (23mm casing) width tire on my roadbike and its rims are still true.

What you will notice, however, is that a 1.25" tire at 70 psi (or a 23c tire at 120 psi!) is a whole lot rougher on the backside than a 2" tire at 40 psi.
 
pizark,

all those sla's are closer to 50 lbs.... with that much weight, I would advise a tire at least 2.00 wide. 1.25 slicks for mountain bikes are not meant to be used with 70+ lbs of bike/kit, 175 lbs of rider, traveling at sustained 23+ mph speeds...

not enough air volume...

also remember the inherent mental conditioning of light n fast bike shop folks not familiar with what works on e -conversions...

go bigger....don't be tempted by a "bargain".....

Peace,

Len
 
Accepting the fact that monetary concerns are real, safety and comfort concerns are just as real. The price of tires is pretty much negligible in the overall cost of an ebike and sacrificing safety or comfort to save twenty bucks may not be a good idea. Plus, properly inflated and maintained tires last a long time. If there's a snowballs chance of a smaller tire being squirrely then it's simply not worth the effort. All this is simply an opinion.
Mike
 
I wouldn't put those on. I run 2.2 Hank slicks from Bontrager. The smaller tire will be harder on the hub motor. Less dampening and motor will resonate more. At least mine did.
 
On my roads slicks would be suicide. Too much gravel. In a more urban setting, where the rocks aren't an inch deep in the corners, maybe ok. I'd rather run more battery than have less tread. It's not going to radically increase your range.
 
I am "safe" and I know about being "slick".

My bikes run 3" wide slicks (24" rims, but the outside diameter is equal to 26" wheels) and they give goobs of traction on the street when it's dry. The moment it rains it's all of a sudden VERY scary because all that traction you got used to when dry isn't there and it has about as much grip as a thin tire.

Slicks are not good in the wet.
 
Miles said:
I don't think aquaplaning is a problem for bicycles.... :p
Click to expand...
It's more of a question of adhesion of the rubber. One of the problems for lightweight motorcycles (like the 50cc road racer classes) is that they have a hard time heating up the tires. The big heavy bikes heat up the tires pretty fast, but they use tire warmers to speed things up anyway.

Back to bikes...

When it gets wet the tires aren't able to get that grip from the tires being hot. My slicks give so much traction on a hot day that my lean angles are close to what you would expect on a motorcycle. It's just that when things get wet that really high limit you got used to all of a sudden is gone and you are left with decent traction for a regular bike, but just don't try to lean much or brake too hard.

One could argue that a little bit of a tread pattern is better overall than pure slicks because it provides a better overall coverage of all conditions.

But I love my (nearly) pure slicks... on a hot day they grip like crazy. :p

02609.JPG
 
safe said:
One could argue that a little bit of a tread pattern is better overall than pure slicks because it provides a better overall coverage of all conditions.
Click to expand...

The consensus seems to be that tread does not increase performance in wet conditions for bicycle tyres.

I've no idea about 3" tyres as used in your micro-niche, though :wink:
 
Miles said:
The consensus seems to be that tread does not increase performance in wet conditions for bicycle tyres.
Click to expand...
I've heard this on the narrow tires that people use to race on like the Tour De France. If your tire is only 1" wide there's just not enough there to begin with to create any sort of tread pattern. Those tires will sometimes have microscopic tread inserted intothem, but it does need not to matter.

When your tire is 3" wide the difference between the high limit (hot dry day) verses the low limit (cool wet day) is so dramatic that it will surprise you.

I'd suggest getting 2.125" slicks rather than 1.25" slicks if you are going to go street anyway... but I like having performance a lot.
 
Miles said:
http://www.sheldonbrown.com/brandt/slicks.html
Click to expand...
Commercial aircraft, and especially motorcycles, demonstrate that a round cross section tire, like the bicycle tire, has an ideal shape to prevent hydroplaning. The contact patch, a pointed canoe shape, displaces water exceptionally well. In spite of this, hydroplaning seems to be a primary concern for riders who are afraid to use smooth tires. After assurances from motorcycle and aircraft examples, slipperiness on wet pavement appears as the next hurdle.

That's why I was dismissing the hydroplaning as an issue. Slicks do offer very good dry weather performance and when the road becomes wet you need to accept that tread or no tread you have far less traction to work with because the pavement gets slippery. I know that water tends to allow oils and rubber that have been laid down previously to rise to the surface and make things very slippery.

In California you have long dry summers where all this oil builds up and the first rain of the year causes all kinds of accidents because this slime makes things really slippery. By the second or third rain things calm down as this gets washed off.

In a place like England that is constantly getting rain year round you would have little build up and probably are prepared for the lower traction levels in the wet. (you get used to it if you ride in it a lot)

I'm now in the Midwest and it rains a lot, but then it dries out really fast because it's hot in the summer. So I'll just wait an hour or two and go for a ride and things are okay.

Being from California originally I'm somewhat paranoid about wet riding... but it's probably not warranted.
 
Miles said:
safe said:
One could argue that a little bit of a tread pattern is better overall than pure slicks because it provides a better overall coverage of all conditions.
Click to expand...
The consensus seems to be that tread does not increase performance in wet conditions for bicycle tyres.
Click to expand...
This was the old argument... I'm okay with the idea that the old argument was wrong.

Fine by me, I use slicks already, so if they are just as good that's all the better. :)

So the moral of all this is that slicks are never worse than having tread if you ride on the street, but that wet pavement is still dramatically more slippery so you still need to be careful.
 
Slicks are fine.
Cheap tires will preform like cheap tires.

But the real issue is stopping.
A narrow tire has a smaller contact patch. The smaller the contact patch, the longer it takes to stop.
And an Ebike is 3 or 4 times the weight of a normal bike.

a lesson I learned way back in the day, when I switched from 25c touring tires to 18C racing tires. 1/4 narrower ment 1/4 longer stopping distance.
 
Drunkskunk said:
But the real issue is stopping.
A narrow tire has a smaller contact patch. The smaller the contact patch, the longer it takes to stop.
And an Ebike is 3 or 4 times the weight of a normal bike.
Click to expand...

Everything else being equal, the contact patch will be about the same area for different sizes of tyre, no?
 
the PSI of a bike tire is the air pressure inside the tire, not the ground pressure.
The contact patch is measured in whats called "ground pressure"
the narrower the tire, the smaller the area in contact with the ground, as shown in my badly drawn pic above. And that raises the Ground pressure, but the air pressure remains the same.

A fat 5 inch balloon tire will have a huge contact patch compared to a 1 inch racing tire, even if they are both inflated to 40psi.
 
Pizark,

The larger the tire width, the more air volume in the tire. The more air volume you have in a tire, the less you need to run it at a high PSI. High PSI = a harder tire, less " tire suspension", and in general more shock on bike and rider. In addition, as stated by others, a larger width tire provides a greater contact patch on the road, increasing handling and stopping effciency. Any slick style tread will suffice until you reach higher than avergae performance levels.

The 1.25 slicks for mountain bikes were originally developed to allow non-electrified mountain bike owners the capacity to gain a bit more speed and efficiency out of their MTB's when riding on the road, rather than having to pony up for road bike...

You can certainly run them, but you just have to be a bit more aware of the lines you pick while riding, and expect flat issues a bit more frequently. The frequency and intensity of these issues will be exacerbated by the increased weight of of the electric conversion kit.

A better tire for your set up is a larger width tire, 2.0 or larger....

Peace,

Len
 
My hub motor hated being in a skinny tire. It resonated more as there is less dampening. Especially on acceleration. Everyone could here me coming. Get Big Hank slicks. I love em. I've inflated mine to proper levels now that they've fixed some of the roads around here.
 
Drunkskunk said:
the PSI of a bike tire is the air pressure inside the tire, not the ground pressure.
The contact patch is measured in whats called "ground pressure"
the narrower the tire, the smaller the area in contact with the ground, as shown in my badly drawn pic above. And that raises the Ground pressure, but the air pressure remains the same.

A fat 5 inch balloon tire will have a huge contact patch compared to a 1 inch racing tire, even if they are both inflated to 40psi.
Click to expand...

The ground pressure would be the weight of the bicycle and rider, divided between the wheels, and...?

So, what determines the size of the contact patch, then?

For a given tyre cross-section, a larger diameter wheel will have a longer narrower contact patch than one of smaller diameter, but the area of the contact patch will be the same......

Air pressure in the tyre certainly increases under load.

So...... assuming a perfectly elastic tyre, and within reasonable limits, surely contact patch area in square inches equals weight of load in pounds, divided by no. of wheels, divided by PSI figure, no?
 
I have 1.62 slicks on my Giant Warp DS, I find they roll nice, but they do not grip as will as mountain bike tires.
 
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