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What really causes these flatspots?

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What really causes these flatspots?

Old 11-04-18, 04:08 PM
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What really causes these flatspots?

These tires don't even have 100 miles on them yet yet I have this flatspots on them. All my rear tires after about 500 miles usually look like this. What causes it besides skidding on one spot? These are Continental Ultra Sport 2.
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Old 11-04-18, 07:02 PM
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Pretty much just locking up the brake and skidding.
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Old 11-04-18, 07:07 PM
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Is it more front or back? Could be rider technique or do you have particularly textured abrasive roads?
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Old 11-05-18, 05:46 AM
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Originally Posted by Le Mechanic View Post
Pretty much just locking up the brake and skidding.
yeah. These tires are so soft though. Uugh.
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Old 11-05-18, 05:46 AM
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Originally Posted by mtbikerinpa View Post
Is it more front or back? Could be rider technique or do you have particularly textured abrasive roads?
Always rear
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Old 11-05-18, 09:35 AM
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If the flattened area encircles the whole tire and is slightly off center, it is probably due to wear caused by the road's crown.
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Old 11-05-18, 11:15 AM
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It's wear. As the tread wears down it will get wider due to the curvature of the tire. Always worse on the rear due to more weight and friction of propelling you forward.
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Old 11-05-18, 12:22 PM
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I suspect the OP is talking about localized areas of greater wear, not the rather consistent wear from general abrasion of the tread cap by the road surface.

If this is correct then what makes localized greater wear? Is the tread/rubber softer, less able to withstand the scuffing that a rear tire goes through (to a greater degree then the front)? Is there greater abrasion at points about the tire's circumference? There are pretty much the only causes of greater tread cap removal.

The tread cap could be softer is spots but given the fairly high degree of production control that Conti, and other manufactures, strive to I seriously doubt this. I have heard of tire rubber becoming softer due to chemical exposure but I also serious doubt this is going on. Parking the bike in a puddle of solvent is quite unlikely.

Varying the degree/amount of abrasion around the circumference is a much more likely chance. The obvious is skidding, whether intentional (like skid stops on a fixed set up) or from momentary wheel lock ups due to rim dents catching on the brake pads. Other possibilities are a wheel/rim with bad enough flat spots so that there's a hop to the tire's movement across the road surface. As the tire is "lifted" off the road and then re compresses down on it the weight/abrasion can change. One would hope both of these possibilities would be noticed by the rider. If a tire's casing is deformed, casing cord or poor seating, it too can cause localized wear. But again both tend tom be easily seen. If the tire is used on a trainer stand and the tire/roller contact pressure isn't enough some slippage under hard acceleration can happen. If enough of this were to happen I guess some local wear could occur, but...

What I can't really know from the photos is how much local wear there is. It seems that the width of the wear band is wider but it's hard to say with complete certainty. I do see some slight line like "things" but I see this on many other tires and always felt these are from road derbies. I would love to have the bike in hand as well as watch the OP ride a bit. Andy
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Old 11-05-18, 12:31 PM
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A single skid on a road tire can easily take off that much rubber. Given that the OP said "Always rear" (and hasn't said that the tire was never skidded), skidding represents by far the most logical explanation.
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Old 11-05-18, 12:46 PM
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Fashionable skinny tires do that. It's a feature you pay extra for.
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Old 11-05-18, 12:54 PM
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OP, I cannot tell if the wear is uniform around the rim or just in one place(s) from you photo that only shows a portion of the tire. If it is in patches and it every tire develops the same worn patches, then this is almost certainly caused by braking. (Yes, really bad hops in the rim could cause issues but I have never seen it.)

If you ride fix gear and skid stop, are you riding with a gear ratio that comes out to an even number? 48-16 becomes 48/16 = 3. This wheel will wear in exactly three places evenly spaced. (They will be the only places the cranks are horizontal. If you change that gear to a 47-16, that ratio is no longer even and over time the wear patches shift.

With caliper brakes, any defects in the rim which "catch" the brake pads will cause concentrated wear at that point. As Andrew said in the above post - dents (usually actually bulges) from impacts with (say) a pothole, issues with the braking surface itself (my one experience with hard anodized rims after enough abuse the anodizing flaked off in places, leaving much more grippy aluminum) and sometimes just the joint of the rim from manufacturing. Metal rims are made from straight extrusion bent into a hoop and joined with either a weld or an inside sleeve. Poor fits at the sleeve and later, distortion from the weld used to be common and wheelbuilder frequently took a file to the rim surface to improve the braking.

So - if a skidding fix gear rider - count those teeth. If rim brakes - use the tire to guide you to the issues on the rim. (Yet another reason to always mount tires so the label is at the valve (or the rim label at the joint directly across. The first reason is so when you flat, you can correlate locations so when you find that tiny hole in the tube from a truck tire wire, you know where to look on the tire to pull it out.).

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Old 11-05-18, 02:01 PM
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Brake lock skidding. As others said, that's common with road bike slicks. Happened with my pricey Schwalbe One V-Guards and inexpensive Continental Ultra Sport II, always the rear tire, always due to emergency braking. Doesn't take much to flat-spot these types of tires.

Stick with the Ultra Sport II. They're good for the money. Only slightly more rolling resistance than my Schwalbe Ones, and the Contis have been less prone to nicks and cuts, and no more vulnerable to puncture flats.

And you can't really tell how tough a tire is from the feel of the rubber to the fingertips. The Schwalbe Ones and Conti Ultra Sport II felt the same to the touch, but the Contis have been tougher yet also grip really well.

"Harder" tires don't necessarily work better. My road bike came with cheap Vittoria Zaffiros. The tires felt hard to the touch, skidded way too easily, were very prone to nicks and cuts and the ride was harsh. For only a few bucks more per tire the Conti Ultra Sport II is a much better tire.
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Old 11-05-18, 08:23 PM
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Originally Posted by canklecat View Post
Brake lock skidding. As others said, that's common with road bike slicks. Happened with my pricey Schwalbe One V-Guards and inexpensive Continental Ultra Sport II, always the rear tire, always due to emergency braking. Doesn't take much to flat-spot these types of tires.

Stick with the Ultra Sport II. They're good for the money. Only slightly more rolling resistance than my Schwalbe Ones, and the Contis have been less prone to nicks and cuts, and no more vulnerable to puncture flats.

And you can't really tell how tough a tire is from the feel of the rubber to the fingertips. The Schwalbe Ones and Conti Ultra Sport II felt the same to the touch, but the Contis have been tougher yet also grip really well.

"Harder" tires don't necessarily work better. My road bike came with cheap Vittoria Zaffiros. The tires felt hard to the touch, skidded way too easily, were very prone to nicks and cuts and the ride was harsh. For only a few bucks more per tire the Conti Ultra Sport II is a much better tire.
Yes. Every Conti Ultra 2 tire has this mark in the rear. It is not a fixed as some have thought. This is a Tigara brake. It is just so fustrating to see especially when it is a fairly new tire. It is a 23mm if that makes any difference.
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Old 11-05-18, 08:36 PM
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Personally, I think the rear brake is almost useless when it comes to hard stops, especially downhill. The harder you're stopping, the less weight there is on the rear and the more likely you are to skid and flatspot.

I run my rear brake so loose that when I press the lever all the way, I barely skid on flats. This makes it easier to not lock the rear. Super important when you're running a $50 tire that's stickier than almost every tire out there.
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Old 11-05-18, 09:32 PM
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Originally Posted by DynoD500_SR20-d View Post
Yes. Every Conti Ultra 2 tire has this mark in the rear. It is not a fixed as some have thought. This is a Tigara brake. It is just so fustrating to see especially when it is a fairly new tire. It is a 23mm if that makes any difference.
There is very little rubber in bicycle tires overall. Skidding them in a stop can easily wear through the rubber of the tread. I once skidded a tire (long ago) for 30 or 40 feet at a high speed and scoured right down to the threads.

Originally Posted by smashndash View Post
Personally, I think the rear brake is almost useless when it comes to hard stops, especially downhill. The harder you're stopping, the less weight there is on the rear and the more likely you are to skid and flatspot.

I run my rear brake so loose that when I press the lever all the way, I barely skid on flats. This makes it easier to not lock the rear. Super important when you're running a $50 tire that's stickier than almost every tire out there.
The rear brake is highly useful but you have to know how to use it. Most people donít. On hard stops, shifting your body weight rearward 3-4Ē and dropping down 2-3Ē will increase deceleration significantly (almost double) and reduces the chances of skidding. On the plus side, you decelerate faster and will more control.

If you donít want to shift weight rearward and downward, then ease up pressure on the front brake and add more pressure on the rear brake. Youíll reduce deceleration (slightly) but youíll brake under more control and not ruin tires.
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Old 11-05-18, 09:47 PM
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Originally Posted by cyccommute View Post
The rear brake is highly useful but you have to know how to use it. Most people donít. On hard stops, shifting your body weight rearward 3-4Ē and dropping down 2-3Ē will increase deceleration significantly (almost double) and reduces the chances of skidding. On the plus side, you decelerate faster and will more control.

If you donít want to shift weight rearward and downward, then ease up pressure on the front brake and add more pressure on the rear brake. Youíll reduce deceleration (slightly) but youíll brake under more control and not ruin tires.
I don't know if we have the same definition of hard stops here. At 40+mph down a 10% grade, if you're trying to bleed off speed before a corner in less than second, sliding back and getting low is a prerequisite to not crashing. I find that the rear brake is far more useful as a heat dump (ie prolonged braking) since I want to conserve my front brake for harder stops. On steep hills, I can't honestly say that the rear brake is incredibly useful for hard braking. I've tried to stop on a 5 or 6% hill with one hand at walking pace (rear only) and it was almost impossible (I started skidding).

If I have to stop really hard even on a flat, I think the optimal braking technique is to just barely have the rear wheel touching (so as to use the adhesive grip of the rear tire), get as low and back as possible, but still heavily rely on the front.

My issue here is that if a large percentage of your braking force is coming from the rear, I can almost guarantee you that you are not stopping as hard as you could. And if the primary concern here is conserving rear tires, then I think my suggestion is pretty valid, even if one does not believe the above statement.
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Old 11-05-18, 10:38 PM
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Originally Posted by smashndash View Post
I don't know if we have the same definition of hard stops here. At 40+mph down a 10% grade, if you're trying to bleed off speed before a corner in less than second, sliding back and getting low is a prerequisite to not crashing. I find that the rear brake is far more useful as a heat dump (ie prolonged braking) since I want to conserve my front brake for harder stops. On steep hills, I can't honestly say that the rear brake is incredibly useful for hard braking. I've tried to stop on a 5 or 6% hill with one hand at walking pace (rear only) and it was almost impossible (I started skidding).
That sliding back on a fast downhill is the same prerequisite to braking better in any situation. Iím not sure why you feel that you can conserve your front brake by not using it. Your brakes arenít limited to the number of times you can use them. On fast downhills, I brake hard with both brakes prior to corners and when I want to scrub speed. I donít drag either brake.


If I have to stop really hard even on a flat, I think the optimal braking technique is to just barely have the rear wheel touching (so as to use the adhesive grip of the rear tire), get as low and back as possible, but still heavily rely on the front.
While it is true that the front brake provides most of the braking power, itís still a good idea to use both brakes. Moving back and down puts the rear wheel in more contact with the ground which improves control and, since the deceleration is increased, provides more braking power over all.

Additionally, if you brake like you describe, you are much more likely to skid the rear tire as you attempt to keep that balance. And, on a thin road tire, that is going to result in flat spots.

My issue here is that if a large percentage of your braking force is coming from the rear, I can almost guarantee you that you are not stopping as hard as you could. And if the primary concern here is conserving rear tires, then I think my suggestion is pretty valid, even if one does not believe the above statement.
I did not, nor would I ever suggest, that a large percentage of braking force comes from the rear. But it is not zero and it is not zero up to the point where the rear wheel starts to lift off. Nor do you get maximum possible braking force until the instant before the rider goes over the bars. No one brakes to that point so it is advantageous to take advantage of the force that the rear provides until such time as it doesnít provide any more
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Old 11-06-18, 12:12 AM
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Originally Posted by cyccommute View Post


That sliding back on a fast downhill is the same prerequisite to braking better in any situation. I’m not sure why you feel that you can conserve your front brake by not using it. Your brakes aren’t limited to the number of times you can use them. On fast downhills, I brake hard with both brakes prior to corners and when I want to scrub speed. I don’t drag either brake.

While it is true that the front brake provides most of the braking power, it’s still a good idea to use both brakes. Moving back and down puts the rear wheel in more contact with the ground which improves control and, since the deceleration is increased, provides more braking power over all.

Additionally, if you brake like you describe, you are much more likely to skid the rear tire as you attempt to keep that balance. And, on a thin road tire, that is going to result in flat spots.


I did not, nor would I ever suggest, that a large percentage of braking force comes from the rear. But it is not zero and it is not zero up to the point where the rear wheel starts to lift off. Nor do you get maximum possible braking force until the instant before the rider goes over the bars. No one brakes to that point so it is advantageous to take advantage of the force that the rear provides until such time as it doesn’t provide any more
My brakes end up overheating on really windy roads. I'm sub 140lbs and very frugal with my brakes and I still find the need to drag them a bit if I'm going down a very bumpy road.

My assertion here is that if one wishes to, they can use their rear brake only for bleeding speed and never for emergency stopping and thus entirely eliminate flat spots, while still not compromising stopping distance much (at all??). I frequently feather the front brake to dance on the (fairly thick) line between OTB and keeping the rear on the ground. It's a little scary, but so is riding fast. It shouldn't be a problem as long as one doesn't turn while braking.

OP: Basically, we're pretty darn sure you're getting flat spots in the rear because you're skidding. If you want to eliminate them, you're going to have to work on your braking technique. You can either learn to get really good at modulating your rear brake (hard, but safe), or rely almost entirely on your front as I do (easier, but definitely more dangerous). Whatever you do, try your best to keep your weight on your rear wheel when braking.
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Old 11-06-18, 12:22 AM
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Originally Posted by smashndash View Post
My brakes end up overheating on really windy roads. I'm sub 140lbs and very frugal with my brakes and I still find the need to drag them a bit if I'm going down a very bumpy road.

My assertion here is that if one wishes to, they can use their rear brake only for bleeding speed and never for emergency stopping and thus entirely eliminate flat spots, while still not compromising stopping distance much (at all??). I frequently feather the front brake to dance on the (fairly thick) line between OTB and keeping the rear on the ground. It's a little scary, but so is riding fast. It shouldn't be a problem as long as one doesn't turn while braking.

OP: Basically, we're pretty darn sure you're getting flat spots in the rear because you're skidding. If you want to eliminate them, you're going to have to work on your braking technique. You can either learn to get really good at modulating your rear brake (hard, but safe), or rely almost entirely on your front as I do (easier, but definitely more dangerous). Whatever you do, try your best to keep your weight on your rear wheel when braking.
If I have to use my brakes to control speed, I use just one for a few seconds, then switch to the other and let the first cool.

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Old 11-06-18, 01:40 AM
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Originally Posted by DynoD500_SR20-d View Post
These tires don't even have 100 miles on them yet yet I have this flatspots on them. All my rear tires after about 500 miles usually look like this. What causes it besides skidding on one spot? These are Continental Ultra Sport 2.
BTW, that flat spot isn't bad at all. I've ridden tires with worse flat spots, nicks and cuts far longer than was sensible. I finally ditched the worst tire when a friend gave my shredded looking Schwalbe One the stink eye. He didn't say much, but I knew what that scowl and grunt meant.

Just keep an eye on it, inspect the flat spot every ride.

If you don't mind the added weight and rolling resistance. Continental and Michelin make some good urban street tires that are a reasonable compromise between lightweight road tires and heavyweight touring/all purpose tires. Check out Continental Sport Contacts, both versions 1 and 2, deeply discounted now at Nashbar and others. Ditto the Michelin Protek Urban. Depending on width they'll weigh around 400 grams, give or take, with thicker tread and puncture shields. I use tires like that on my hybrid. They stand up to hard braking, rough pavement, gravel, whatever, but don't feel like lead filled garden hose. The tricky bit is finding the sweet spot in tire pressure where they feel comfortable but not sluggish.

Or just stock up on Conti Ultra Sport II whenever they're on sale and replace 'em as needed. They're pretty danged good tires for around $15 each, sometimes less on sale. I paid $10 for a wire bead 700x23 Ultra Sport II recently to fill out a Nashbar order to get the $49 minimum for free shipping. Next time I replace the rear 700x25 Ultra Sport II on my road bike I'm gonna try the 700x23 wire bead version just to see if I can feel any difference. It's a wee bit heavier than the folder, but being a narrower version I may not notice any difference at all.

Problem is, the Ultra Sport II lasts a lot longer than I'd expected. I really figured I'd wear out the rear by now, but I didn't ride my road bike as much outdoors this summer after being hit by a car in May. But I did put the equivalent of 200-400 miles a month on the Cycleops trainer on that tire, and the spinning metal drum didn't shred the tire or cause unusual wear. I'm pretty impressed with these cheapo Contis.
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Old 11-06-18, 03:13 PM
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Originally Posted by smashndash View Post
My brakes end up overheating on really windy roads. I'm sub 140lbs and very frugal with my brakes and I still find the need to drag them a bit if I'm going down a very bumpy road.
In 40 years of bicycle riding from road downhills to mountain downhills to mountain bike downhills to loaded touring downhills to riding tandems downhill, I have never overheated a brake of any flavor...cantilever, dual pivot, single pivot or disc. I'm about double your weight...and more than that with a touring load. I don't hold back on downhills either. I don't drag brakes at all even on mountain bike downhills. I get on the brake, scrub speed quickly and then get off the brake. Repeat as necessary. Brake pads can last for years even on my loaded touring bike.

Originally Posted by smashndash View Post
My assertion here is that if one wishes to, they can use their rear brake only for bleeding speed and never for emergency stopping and thus entirely eliminate flat spots, while still not compromising stopping distance much (at all??). I frequently feather the front brake to dance on the (fairly thick) line between OTB and keeping the rear on the ground. It's a little scary, but so is riding fast. It shouldn't be a problem as long as one doesn't turn while braking.
​​​​​​​
If you know how to brake, you can use both brakes effectively and get more out of the brakes in general. For example, I never inadvertently skid the rear tire because I push off the back of the bike and get to the point where the rear doesn't skid. I know how to ride down hills fast. Been doing it all my life. I also know how to use both brakes so that my braking is more effective.

Originally Posted by smashndash View Post
OP: Basically, we're pretty darn sure you're getting flat spots in the rear because you're skidding. If you want to eliminate them, you're going to have to work on your braking technique. You can either learn to get really good at modulating your rear brake (hard, but safe), or rely almost entirely on your front as I do (easier, but definitely more dangerous). Whatever you do, try your best to keep your weight on your rear wheel when braking.
You simply aren't understanding. You keep suggesting that I'm somehow suggesting that DynoD500_SR20-d rely on his rear brake, perhaps exclusively. I'm not. Use both brakes effectively. Relying on either front or rear is not the best way to use the brakes on the bike. Relying on both will let you control the bike better. If nothing else, using the rear brake in conjunction with the front will tell you when the rear has lifted off the ground and warns to that you are on the way to going over the bars. Once the rear has lifted, you are on a unicycle with a pivot in the middle...not exactly the most stable place to be.
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Old 11-06-18, 07:31 PM
  #22  
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Originally Posted by canklecat View Post
BTW, that flat spot isn't bad at all. I've ridden tires with worse flat spots, nicks and cuts far longer than was sensible. I finally ditched the worst tire when a friend gave my shredded looking Schwalbe One the stink eye. He didn't say much, but I knew what that scowl and grunt meant.

Just keep an eye on it, inspect the flat spot every ride.

If you don't mind the added weight and rolling resistance. Continental and Michelin make some good urban street tires that are a reasonable compromise between lightweight road tires and heavyweight touring/all purpose tires. Check out Continental Sport Contacts, both versions 1 and 2, deeply discounted now at Nashbar and others. Ditto the Michelin Protek Urban. Depending on width they'll weigh around 400 grams, give or take, with thicker tread and puncture shields. I use tires like that on my hybrid. They stand up to hard braking, rough pavement, gravel, whatever, but don't feel like lead filled garden hose. The tricky bit is finding the sweet spot in tire pressure where they feel comfortable but not sluggish.

Or just stock up on Conti Ultra Sport II whenever they're on sale and replace 'em as needed. They're pretty danged good tires for around $15 each, sometimes less on sale. I paid $10 for a wire bead 700x23 Ultra Sport II recently to fill out a Nashbar order to get the $49 minimum for free shipping. Next time I replace the rear 700x25 Ultra Sport II on my road bike I'm gonna try the 700x23 wire bead version just to see if I can feel any difference. It's a wee bit heavier than the folder, but being a narrower version I may not notice any difference at all.

Problem is, the Ultra Sport II lasts a lot longer than I'd expected. I really figured I'd wear out the rear by now, but I didn't ride my road bike as much outdoors this summer after being hit by a car in May. But I did put the equivalent of 200-400 miles a month on the Cycleops trainer on that tire, and the spinning metal drum didn't shred the tire or cause unusual wear. I'm pretty impressed with these cheapo Contis.
Ribble has them for $6.00...I am stocking up
https://www.ribblecycles.co.uk/conti...tyre/#pid=9001
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Old 11-06-18, 07:39 PM
  #23  
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Yeah I am suspecting a single skid but that much is disheartening. And this is every rear tire I have.
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Old 11-07-18, 12:00 AM
  #24  
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Well, then stop doing that ... use the front brake, more ..and pay attention,!

slow down earlier..
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Old 11-07-18, 03:56 PM
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Originally Posted by DynoD500_SR20-d View Post
And this is every rear tire I have.
There it is -- there's the clue.
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