Is it bad to run a slightly smaller tyre?

[jafagsx250]

Was surfing the Internet for various tires and prices in preparation of getting new ones when the current one's wear out and came across a nz website biker bargains selling a set of Pirelli sport demon's for 300 bucks. The front tire is the same size as my bike's but the rear is a 140 70 17 rather than a 150 70 17.

Would this be unsafe? Is it better for cornering? I have had a Google search but nothing useful came up.

Thanks

[Ulsterkiwi]

dont know about unsafe, the smaller tyre will definitely make cornering different.
There are plenty on here who know more but my understanding is your tyre choice will be determined by the wheel you have on as much as anything. Some wheels will happily accommodate the slimmer tyre, some may not.
I would strongly suggest talking to someone who actually sells and fits tyres.

[jafagsx250]

dont know about unsafe, the smaller tyre will definitely make cornering different.
There are plenty on here who know more but my understanding is your tyre choice will be determined by the wheel you have on as much as anything. Some wheels will happily accommodate the slimmer tyre, some may not.
I would strongly suggest talking to someone who actually sells and fits tyres.

Thanks man. I will definitely do that when it comes to replacing the tires.

[AllanB]

You will find the slightly smaller tyre (10mm narrower) will also have less circumference so the engine will rev slightly higher for any given speed - ie say it sits on 4000rpm at 100 now it may spin at 4400 at 100 with the 140 tyre. On your GSX250 (?) you'll know if this will annoy you as the smaller bikes tend to buzz at high revs.

You'll find it accelerates slightly quicker as a result of the altered gearing as well, again with a small engine that tends to spin up quickly you'll be clicking through the gears slightly quicker.

The arse end of the bike will be slightly lower. You will find the narrower tyre will make the bike turn in quicker.

One thing I'd check - do you use all the rear 150 now - as in no chicken strips? If you are riding to the edge of the 150 I'd question the 140 as you may find she gets a bit squirmy on the edge of the smaller rubber.

Rim size - a Google will assist here - check the 140 is fine on your rim width (rim width will be cast on your rear wheel).

Years back I had to run a 120 instead of a 130 rear on a 750 as the larger size was not in the country. Went absolutely fine with the above to note - the most annoying thing I found was the higher revs.

Plus everyone knows fatter tyres just look cooler

[jafagsx250]

I sold the gsx250 :bugger: . It was a good bike to learn on but wanted something newer to get to uni and around Auckland. So I got a 2008 hyosung with 4000 kilometers on the clock. Which now has the front brake permanently engaged. Which incidentally was why I sold my old one. (didn't want something which was going to be a problem child) So much for that bright idea lol. My brother had one with no issues so I thought I'd be sweet.

I spend a lot of time on the motorway and with the wet roads don't go to the countryside as much as I used to a couple months ago. I still have chicken strips on the 8 year old original stock tires as I don't trust them in the wet weather we have been having lately. On the dry they're fine so I am planning on getting new tires ASAP. Probably Bridgestone bt45 in the correct sizes for 420 dollars. They're only 30 bucks more than the sport demon's will cost all up. And with the harder center compound should last a decent amount of time on the motorway.

It seems to turn in pretty well as is but I don't have anything sporty to compare it to.

It does look pretty mint from the rear with the fat tire.

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[YellowDog]

You need to take care that you don't alter the balance of the ike. I guess it dfepends upon the sort of riding you'll be doing.

Allan's comment over the wheel speed, revs, gears, & acelleration are all correct. Your speedo will also show faster than you are actually doing

[mouldy]

If you are not getting to the edge of the 150 the 140 will be fine and you might be able to reduce your chicken strip . if you do get to the edge of the 150 you may drift the 140

[jafagsx250]

That's a good point. It seems to handle fine with the stock sizes and feels easy to flick into a corner.

It gets quite vibratory at 100 kilometers an hour. But being a hyosung I need am optimistic speedo lol.

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[mouldy]

Bridgestones are definetly the go for the Hyo . Front brake issues could be dry sliders or too much fluid in master cylinder . Always check level is below max mark

[jafagsx250]

Bridgestones are definetly the go for the Hyo . Front brake issues could be dry sliders or too much fluid in master cylinder . Always check level is below max mark

dry sliders the things that that the brake pads move along when the piston pushes it out of the caliper and onto the disc right?

The brake fluid looks fine. I'll have another check after work but I think I have narrowed the brake issue to the caliper not being completely straight. The brake pads are on an angle and not fully back in when the brake lever isn't pulled in.

[Asher]

Some food for thought.
I had a KTM RC390 which comes with a 150/60/17 from factory, but even at elbow dragging lean angles it would still have chicken strips on the rear tyre (non on the front). Lots of people (including racers) swapped the rear tyre to a 140 and it improved the handling and they could get rid of their chicken strips.

A Hyosung 250 has barely enough power to pull the skin off a rice pudding so a 140 should be fine in that respect, but the smaller tyre might sit flatter on the rim which isnt ideal.

If you have Chinese made levers they are notorious for causing your front brake to lock on.

[Crasherfromwayback]

If you are not getting to the edge of the 150 the 140 will be fine and you might be able to reduce your chicken strip . if you do get to the edge of the 150 you may drift the 140

Bridgestones are definetly the go for the Hyo . Front brake issues could be dry sliders or too much fluid in master cylinder . Always check level is below max mark

You need to stop reading internet forums. And start wearing a fucking bib.

[Crasherfromwayback]

Some food for thought.
I had a KTM RC390 which comes with a 150/60/17 from factory, but even at elbow dragging lean angles it would still have chicken strips on the rear tyre (non on the front)..

You too, need a fucking bib.

[jafagsx250]

Some food for thought.
I had a KTM RC390 which comes with a 150/60/17 from factory, but even at elbow dragging lean angles it would still have chicken strips on the rear tyre (non on the front). Lots of people (including racers) swapped the rear tyre to a 140 and it improved the handling and they could get rid of their chicken strips.

A Hyosung 250 has barely enough power to pull the skin off a rice pudding so a 140 should be fine in that respect, but the smaller tyre might sit flatter on the rim which isnt ideal.

If you have Chinese made levers they are notorious for causing your front brake to lock on.

they're the factory levers so i'm not sure if they're much better. it's getting fixed on thursday though. apart from the sticky front brake and old shinko's i quite like it for what it is.

[Drew]

You need to stop reading internet forums. And start wearing a fucking bib.

Glad you said it bro. I get it wrong sometimes, but these cunts just don't understand bikes at all methinks.

Regarding tyre size and increased revs for same speed. Circumference of the 150 is 66.3 inches. The 140 is 65.5 inches. Work the percentage difference of those two numbers, that's the same percentage of the original revs at a set speed that will increase. It's no where near 10%.

Will it upset the bike's handling? Likely not. Likely any noticeable difference will be entirely in the riders head.

Check what size rim the tyre manufacturer says the hoop can go on. They will give a minimum and maximum.

For the love of fuck, ignore your chicken strip. They mean fuck all! I've done a half decent lap on a couple different bikes when I thought I was a bike racer, and there seemed to be no correlation between getting to the edge and my lap time.

It's a pissing contest. Dreamed up by heroes who wanna wank on about how great the are on a bike. Dukie is the kinda fucktard that points out his lack of chicken strip. You DO NOT want to be like Dukie.