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 Post subject: CBR 125 Tyre Choice
PostPosted: Wed Jun 18, 2014 9:32 pm 
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Performance Pack

Joined: Tue Mar 25, 2014 3:21 pm
Posts: 35
Australia
I know this is a topic likely to be as polarising as Religion and Politics, but here goes!
:laugh:
Our 125 has standard IRC tyres - it's not yet done 5000 km and the tyres are unsurprisingly, like new. they're also 4 years old. And hard. :wink:
Bronnie had a wet session on the track last Sunday and at very moderate speed and lean, suffered a rear wheel lose that resulted in a drop, broken front brake lever and a few rashed parts. :wacko: No biggie and she was right to go out in the very next session (Yay Dainese! Yay Shoei!). :biggrin:
But the end of the day, the weather had fined up but was still cold (a biting 16 deg C!) with blustery wind. :sad: The track was dry and although she's not there to race, I ran a watch on her and she took a measured 20 secs a lap off her earlier time, clocking a fastest of 1.35 :biggrin: - which is also a PB for her. Certainly the bike is capable of more, but she's learning - as am I, as her chief spanner-monkey. :rolleyes:
A lighter, freer-flowing pipe now means we can hear when she gets out of the throttle and where she's changing gear; she now has a rev-counter and knows what the rev-limiter sounds like: it's a gradual learning curve and she's not there to race - even though a smaller kid on a racing two-stroke Metrakit was giving her the occasional hurry-up and she was determined to stay in front...
Next steps are some braided brake lines (in the air on their way here right now) - and new tyres.

But which new tyres?
My own track-day experience would probably stop at Metzeler Komp K ME 33 & 99 and Dunlop slicks; I know a lot more about dirt and ADV tyres nowadays.

I'm reluctant to go up a size over OEM on the Honda, as there will certainly be handling ramifications that a novice won't automatically know how to ride around - plus I'm reluctant to introduce new issues that may have startling implications on a very small bike. My 250 GP bike was lighter than the CBR and any changes would have profound effects on other, apparently unrelated parts of the bike.

The CBR125's stock 80/90 17 fr, 100/80 17 r tyres aren't that easy to source: I've been told that currently, Bridgestone do the stickiest small-bike tyres - but the local importer doesn't bring in such small hoops.
Demand is clearly low: at the motorcycle wrecker I almost never need to visit in the days after a track session, there are about a dozen crashed CBR125s lined up, all with similar damage (front & side fairings busted up, headlamps gone), all with under 20,000km on the clock (some with a LOT under 20k!) - and all seem to have the original OEM tyres still in place. You can understand an importer being reluctant to bring in a container-load of skinny tyres that almost no-one wants....

The best I've found are Pirellis - a SportDragon for the front and an MT75R for the rear, in the correct sizes, or Continental 44P (f) and 52P (r).

Has anyone here used either of these tyre combos? If so, I'd love to hear your impressions - longevity isn't an issue!

Also, on the current "Interesting Rubber Company" tyres, she's getting some feathering on the edges of the front tyre, but not on the rear; intuitively, I'd say that indicates she's working the front harder and could do with more ride hieght at the front (or less at the rear?) and perhaps more air-pressure, or perhaps slightly stiffer forks.

Any suggestions?
Thnx!


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 Post subject: Re: Tyre Choice
PostPosted: Wed Jun 18, 2014 10:34 pm 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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Precis wrote:
Also, on the current "Interesting Rubber Company" tyres, she's getting some feathering on the edges of the front tyre, but not on the rear; intuitively, I'd say that indicates she's working the front harder and could do with more ride hieght at the front (or less at the rear?) and perhaps more air-pressure, or perhaps slightly stiffer forks.

Any suggestions?
Thnx!


The only tires I would recommend are Metzeler Interac M5's in a 110/70/ZR17. I'm on my fourth set now, and for rain, they are unreal. Also, for handling, they are beyond the limits of the bike. I really can't see anyone being able to get the bike past these tires.

The rim sizes on the first gen bikes (and even the second gen bikes) makes it really hard to find good tires. In the M5's case you're running two front tires. Lifespan is good but the front can get a little lumpy, usually after a long while. The ideal would be to rotate the front to the rear when replacing the rear.

Also, they fall in just beautifully when new. This only lasts for 500K or so. Because the tires are wider then the rim they are nice & pointy when new. Once they get some miles on them the points unfortunately wear down a bit and you loose some fall in. But, for the first 500k or so they are unreal. Even after that point they are awesome. I do all sorts of crazy things on them and have pushed them, once or twice, into some really hairy situations and I'm quite sure the frame on the bike will bend from lateral g-force loading before those tires loose traction :cool: From a safety standpoint they should be a requirement. Rain? People have and do put their knee down in the rain. The tire is actually designed for 150 HP+ high-end litre bikes....

Really, when it comes right down to it, you have the worst tires in the world on the bike :tongue: . They are bias plies (I remember those!) and changing over to M5's puts you into one of the top 3 radials out there (I think). That alone is a massive change. The wet weather performance was critical for me because when I was learning to ride the IRC's almost killed me twice on one trip. First thing I did when I got home from that ride was research. I actually tested the M5's by intentionally going out in a torrential downpour. Through the twisties around a lake with a 30 knot cross-wind and sheeting rain blowing sideways with a fully drenched road (hydroplane material). It turned out to be one of my best rides ever! I went from being paranoid in the rain (due to almost being killed twice) to looking forward to it.

Another issue the 110's address is the nervousness or twitchyness of the bike on the highway with cross-winds. That disappears with the 110's. Another is the bikes' tendency to fall in cracks and get stuck in them. That also disappears.

If you choose to go this route then you will find that installing them is a horrible job. They are Z rated and I routinely have to inflate them to 110 PSI to seat the beads (don't tell anyone!). The last time I did them I had my neighbor help me and when seating the beads he hides behind the car - the far side of the car :biggrin:

Also, with stock suspension settings and the 110's the bike will NOT want to fall in. I'm talking, you can drive down the road and read a book and not even bother looking up. It will track dead-straight and all cornering will be done straight up. So, to address this you need to change the trail. To do that you just need to lower the bike in the front forks. I'm running, if memory serves, 33mm of exposed fork (if interested I can measure it easily and tell you for sure). This restores the fall in to similar to stock and you can no longer read a book while riding.

You can also adjust the front pre-load by lifting the front of the bike by the handlebars and removing the stock 100mm inserts at the top of the forks. Depending on your daughter's weight you can sub in PVC tubing cut to suit. In my case, I weigh in at 180+ gear so 110mm was perfect for me. If your daughter is the same weight as the average Asian then you may not need to adjust the pre-load. I believe I calculated it out once to see just what they designed the bike for and I think it was spot on a 100 pound rider...... :blink:

Once a person has done that the bike will be totally new. It's an entirely different bike. It will out handle everything on the road. I've blown away a 2010 R6, a 2008 CBR 600 RR, too many Harley's to count, Buell's, and numerous others. The Performance Pack / Suspension Mods / Tires are really cheap and pay HUGE dividends. I'm not kidding when I say my bike will out handle everything. Pick the right road (short straights and tight corners) and you're gone. One day I'll enter it at MotoGP 3 at Phillip island :laugh:

BTW, if you elect to go with 110's a common (and more/less required) tire pressure scheme is 28 front and 40 rear. I did a lot of testing on that and those really are the magic numbers. I don't think you can get stock size tires that will do what you want. In the UK you could get Michelin's in the stock sizes but not here. In all truth, after going Metzeler I can't see any reason to look further other then for a change. I believe you can also get BattleAxe's in the 110's as well in AUS.

Good to hear you daughter is having fun and OK after the spill! :top:

This was a mild run of the bike with the Metzelers, the suspension mods, the Performance Pack and the camshaft...the real corners are about 1/3 of the way through.

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...because every day is MotoGP day when you own a CBR 125r...


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 Post subject: Re: Tyre Choice
PostPosted: Thu Jun 19, 2014 6:54 am 
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Clutch Springs
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One thing many people need to keep in mind is that new(ly) installed tires really need to be “scrubbed” before really pushing the bike.

When tires are manufactured, they use a release agent in the tire molds in order to facilitate their easy remove. That agent is still on the tires when you receive them (the tires have a slick and/or sticky feeling to them). You could give them a good washing before installation, but I believe that at least some of that release agent on the bead aids in the installation on some rims.

Once installed on the bike, you should put at least 100km (more would be better) of “road time” on them. Don’t take corners too hard (i.e. trying to drag the knee), ride on different surfaces types if possible.

What this all does is it facilitates the “scrubbing off” of the release agent and at the same time, ruffs up the tire facing surface. This all helps to improve road grip which of course helps to improve rider safety…


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 Post subject: Re: Tyre Choice
PostPosted: Tue Jul 08, 2014 7:18 am 
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Performance Pack

Joined: Tue Mar 25, 2014 3:21 pm
Posts: 35
Australia
Well, actually finding ANY tyres the right size has proved interesting! Because the bike needs to remain standard and because I don't want to introduce any handling quirks, I have to stick to the factory-listed standard sizes.
But tomorrow we are getting Pirelli Sport Dragons fitted; I'll scrub them in on the balancing machine with a rasp, and we have another track session on Thursday - though after her last drop, Bronnie is a bit nervous of the rain, and it looks likely to tip down that day. We shall see.

Other features (for a different event) we've had to fit are metal tyre valve stems, a steering damper, a metal chain guard and a metal strap to retain the battery. we also need to fit a good-quality lanyard kill-switch, so that if she comes off, the ignition cuts. I know it has a tilt switch, but them's the rules!


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 Post subject: Re: Tyre Choice
PostPosted: Tue Jul 08, 2014 11:41 am 
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Racing ECU (!!)
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Yeah, I've often thought about how much I really need a steering damper for my bike :laugh: :wacko:

When the CBR125 Challenge Series was being put on over here by Honda they installed 110's and altered the suspension. Rules are rules but I draw the line at rider safety. Which kind of sounds funny when you think about it :blink: but I don't mess with the rain. Sorry to hear your daughter went down in the rain and wish they could run a better tire for that kind of riding :smile:

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 Post subject: Re: Tyre Choice
PostPosted: Wed Oct 29, 2014 11:16 am 
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Performance Pack

Joined: Wed Oct 22, 2014 6:07 pm
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Canada
Hi guys,

I have a 2011 cbr 125r and I plan to replace the tires on them this winter. Im new to riding and want the best grip I can get on wet roads. I avoid the rain with the stock tires, but enjoy riding too much to let a little rain stop me :biggrin: . So over the winter I plan to do a few things to the bike which include installing the performance pack (I will be ordering any day now!), and new Metzler tires (they sound great).
I will be getting the 110s for the front, not sure if I should get the same for the back.my bike tyre is 130/70-17 . I cant find a 130, would it be bad to go to the next size available which are 150s or go down to 120s. Any advise is great.

Thanks!


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 Post subject: Re: Tyre Choice
PostPosted: Wed Oct 29, 2014 12:52 pm 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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That's a smart plan. The difference between stock tires and a high-end, high quality tire are unreal and this relates directly to safety (especially in the rain) and also to high performance riding in the dry (or both!) :laugh: I know from experience it's money well spent and it should be the very first thing a new rider does because it increases safety to such a degree that I'm certain accident rates would drop like a rock if everyone followed the same logic. So good on ya for being smart :top:

Having said that, with the CBR 125 we are saddled with goofy rim sizes which means tire selection tends to be limited. I cased it for my bike (the first gen bike) with 110's front & rear in a Metzeler Interac M5. An absolutely unreal tire, I cannot for the life of me fathom how a person can have an accident with them on unless they were asleep at the time. Even then, they provide such a huge margin of safety you should be able to sleep and ride with no issue :laugh:

Your bike, being a second gen bike, uses wider rim sizes. While still not perfect they do open the door to more variety then a first gen owner. I don't know what to suggest other then that if you can get into Metzeler with a high silica content you should be good in the rain.

It looks like you can get ME 880's but they are designed for fat and heavy touring bikes :sad: so they would probably be the equivalent of running a truck tire :laugh: You could go Lasertech front & rear - that would be a better choice. It's a high silica tire so it would be great in the rain. But my preference would be a sport/touring or sport tire with a high silica content. It's too bad because it looks like your rim sizes preclude running the M5 or the M7 - they would be my first choice and you'd never need to go down the 'what tire to run' decision again.

It's a tough one. Do as much research as you can to see what fits. You can generally go up 10mm front and rear with no real side effects so that will open the door to more selection.

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Marvin Miller
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 Post subject: Re: Tyre Choice
PostPosted: Wed Oct 29, 2014 4:45 pm 
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Performance Pack

Joined: Wed Oct 22, 2014 6:07 pm
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Canada
Marvin,

Thank you, for the advise. I will definitely check out some of the tires you mentioned and also do more research. I will post back on what i end up getting.


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 Post subject: Re: Tyre Choice
PostPosted: Thu Oct 30, 2014 3:52 am 
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Performance Pack

Joined: Tue Mar 25, 2014 3:21 pm
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Australia
150 is waaay too wide for a 125; frankly, a 130 is too wide; if nothing else, the tyres will be made for bikes two or three times the weight of yours, so the tyres will never start to work properly - they need mass and friction to generate heat and the mighty CBR won't generate enough of either to do much more than polish the tyre - exactly what you don't want in cold and rainy conditions. We've had good success with Pirellis - though our conditions are hotter and drier than yours!


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 Post subject: Re: Tyre Choice
PostPosted: Thu Oct 30, 2014 9:24 am 
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Precis wrote:
150 is waaay too wide for a 125; frankly, a 130 is too wide; if nothing else, the tyres will be made for bikes two or three times the weight of yours, so the tyres will never start to work properly - they need mass and friction to generate heat and the mighty CBR won't generate enough of either to do much more than polish the tyre - exactly what you don't want in cold and rainy conditions. We've had good success with Pirellis - though our conditions are hotter and drier than yours!


He's got a second gen bike so it comes stock with 100 / 130 rims. I've had no issues running Interac M5's on my bike, they were designed for much larger and more powerful bikes. They heat up so fast that when I pull over in the rain it's common to see them steam and for the rain to dry on the tire - fast. That's where the steam is coming from - the rain being burned off the tire. It's really something to see. It's readily noticeable, in all weather, how hot the tire is when you touch it. They work - and they work better then any other tire I've seen on this bike :top:

Unfortunately, it doesn't look like you can get them in your 100 / 130 sizes - or even 10 over :sad:

Tire heat is more related to the rubber compound used in the tire rather then the weight of the bike, as a general principle but it is worth keeping mind at some level.

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