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I'm looking into race tires but seems there are none that will fit the Z easily.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/dunlop-tt93-mini-race-scooter-tire

The Dunlop front will fit just fine, but the rear option I fear will be too large and hit the chain. The 120/80 rear would mean a side wall height 96mm compared to 84mm stock.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/michelin-bopper-scooter-moped-tire

Michelin has a rear fit but a low and wide front option.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/conti-zippy-1-performance-scooter-tire

Conteniental has a rear that might work, but no matching front size.

Hoping someone comes along soon and gives us a proper set. Will keep an eye out for options.
 

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Best thing is definitely to keep an eye out and find out if there are other models with similar sizings like the Grom. You may find proper race tires hard to find for a 12" rim. It may be also worth emailing the manufacturers of the tyres you like on your bigger bikes for racing and see if there's any options they can suggest or if they make them. You may find they make them but don't have many retailers that carry them? Just a few suggestions.
 

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I'm looking into race tires but seems there are none that will fit the Z easily.

Hoping someone comes along soon and gives us a proper set. Will keep an eye out for options.
Mitas has Race Tires that will fit the Z125.

The MC-35 comes in a 100/90-12 and is available in a Medium, Soft or Super Soft compound.

The MC-34 comes in a 120/70-12 and is available in Supersoft compound.

Mixing the 2 tire models (MC-35 front & MC-34 rear) shouldn't be a problem as long as you match compounds.

The MC-35 also comes in a 120/80-12 that would raise the rear of the bike about .5", that might make the steering a bit quicker, which isn't a bad thing for racing. The sidewall height is .47" taller, which would soften the ride very slightly.

These tires are available on eBay now. Use "Mitas Race Tires" as the search

Here's the catalog. Scroll down to page 21 for their scooter race tires.

http://mitas-moto.com.omega.nen.cz/underwood/download/files/mitas_katalog_en_es_web.pdf

Here's one eBay listing:

Mitas MC35 s Racer Racing Tires 120 80 12 and 100 90 12 Pair Medium Super Soft | eBay

mz.jpg
 

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I'm looking into race tires but seems there are none that will fit the Z easily.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/dunlop-tt93-mini-race-scooter-tire

The Dunlop front will fit just fine, but the rear option I fear will be too large and hit the chain. The 120/80 rear would mean a side wall height 96mm compared to 84mm stock.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/michelin-bopper-scooter-moped-tire

Michelin has a rear fit but a low and wide front option.

http://www.bikebandit.com/tires-tubes/motorcycle-tires/conti-zippy-1-performance-scooter-tire

Conteniental has a rear that might work, but no matching front size.

Hoping someone comes along soon and gives us a proper set. Will keep an eye out for options.
as in the Dunlop rear.....that's only about less than half an inch (.472) in diameter bigger....less than a quarter on an inch (.236) per side, should be no problem at all. The tire will be taller but not wider.... Those are the tires I will be using
 

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as in the Dunlop rear.....that's only about less than half an inch (.472) in diameter bigger....less than a quarter on an inch (.236) per side, should be no problem at all. The tire will be taller but not wider.... Those are the tires I will be using
Here's the comparison

https://www.tacomaworld.com/tirecalc?tires=120-70r12-120-80r12

Diameter of the 120/80-12 is actually .94" greater, so it is .47" greater from axle center to the ground (and .47" from axle center to top of the tire) so it raises the bike .47" in the rear, not .23", but still insignificant.

Mitas (or Sava, same tire, different name) are GREAT tires. I've had them on 3 bikes I've owned (2 currently) and highly recommend them.
 

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Here's the comparison

https://www.tacomaworld.com/tirecalc?tires=120-70r12-120-80r12

Diameter of the 120/80-12 is actually .94" greater, so it is .47" greater from axle center to the ground (and .47" from axle center to top of the tire) so it raises the bike .47" in the rear, not .23", but still insignificant.

Mitas (or Sava, same tire, different name) are GREAT tires. I've had them on 3 bikes I've owned (2 currently) and highly recommend them.
let's break it down.......
120x.8=96
120x.7=84
a difference of 12mm or .472
that's .236 on the bottom half of the tire and .236 on the top half of the tire to equal .472 total. The bike will be .236 taller in the rear. Think in terms of radius not diameter.
 

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let's break it down.......
120x.8=96
120x.7=84
a difference of 12mm or .472
that's .236 on the bottom half of the tire and .236 on the top half of the tire to equal .472 total. The bike will be .236 taller in the rear. Think in terms of radius not diameter.
See the comparison again. It shows both tires diameters. The 120/80-12 tire is .94" taller in diameter but it will only raise the bike by half that amount (the radius), which is .47".

You're computing the sidewall heights. The 70 in 120/70-12 is the ratio of the sidewall height to the width. 70% of 120 IS 84mm/3.30" sidewall height and 80% of 120 IS 96mm/3.78" sidewall height (see the comparison again).
So that's a sidewall height difference of .47", BUT there are TWO sidewalls on the tire, directly across from each other. The tire is .47" greater in diameter above the axle and .47" greater in diameter below the axle, so raises the rear by .47"

It's easiest in a size comparison to just take half the difference in diameters to see how much a tire will raise (or lower) the rear.
 

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We just wanted to share some information with you all being that our team member @Mlow125, purchased some used tires of a buddies grom this weekend and was able to fit them up perfectly. Front - 100/90/12 and Rear - 120/80/12. No clearance issues and seem to be tires you can get pretty easily. We have order sa set of TT93's in that size to test at the track this weekend so stay tuned for a review on that!
 

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Anyone can comment about the stock tires? For my country it's IRC brand tires, I don't know the model. Also, for riding at go-kart track or for spirited back-road riding, what is the recommended PSI for say a 70-80kg rider? I read the manual, it says 22 PSI front, 29 PSI rear, my guess that is for normal/daily use.

Appreciate any feedback on this, thanks!
 

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sorry to revive such an old thread here, but does going with a larger rear tire height change the dynamics of the bikes control on the track?
 

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as in the Dunlop rear.....that's only about less than half an inch (.472) in diameter bigger....less than a quarter on an inch (.236) per side, should be no problem at all. The tire will be taller but not wider.... Those are the tires I will be using
No, he said the sidewall height, not the diameter! So, it's 1/2" taller on the RADIUS, not diameter. That's significant for both:

- Chassis geometry for steering

- Gearing effect - the 1/2" larger RADIUS causes about a 5% TALLER "gearing" effect. (Exactly like putting on a 5% smaller rear sprocket)

Jim G
 

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Here's the comparison

https://www.tacomaworld.com/tirecalc?tires=120-70r12-120-80r12

Diameter of the 120/80-12 is actually .94" greater, so it is .47" greater from axle center to the ground (and .47" from axle center to top of the tire) so it raises the bike .47" in the rear, not .23", but still insignificant.

Mitas (or Sava, same tire, different name) are GREAT tires. I've had them on 3 bikes I've owned (2 currently) and highly recommend them.
A half inch height increase at the rear is significant on a bike with a short 4 foot wheelbase!

Jim G
 

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You should probably be more concerned about the gearing change than the chassis dynamics. The bike is already twitchy at high speed. Might get a little more twitchy with a little steeper rake but probably not a big deal.

On the other hand a taller rear tire would offer a little more cornering clearance. It's just trade offs.
 

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We have had good luck with the taller 120/80-12 rear tires on our Z125 endurance racer. First year we ran TT93s, then PMT slicks and now Kenda KD1s in that size and the reasons are as others have mentioned above. The taller size rear quickens up the steering(the whole team says it handles better) without any sign of twitchiness even on the longest straights(some over 70 mph), but then, our suspension is also dialed in. The gearing had to be lowered(13/34) but that's easy and the added ground clearance while minimal, is helpful(see below). We tried the OEM 120/70-12 size but it overheated after 30+ lap sessions while the heavier 120/80-12 stayed consistent for 12+ hours at the recent UMRA 24 hrs race. This year we managed almost 1100 laps and we only used 2 sets of Kenda KD1 tires. So I say try the taller tire size on the track and you might like them. We do!

https://www.facebook.com/unitedminiracingassociation/
 

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That picture is freaking me out. You have two left legs! Ok, it took me a while to realize there was a guy in front of you, hahah.

The overheating comment might be regional. So far I've only been running TT93's but up here in WI they won't overheat even if run at very low PSI. I might try the PMT's next year. Maybe I'll go tall in the rear but it's the tight chicanes that the bike seems so flickable as it is that I may end up on my ***.
 

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The overheating comment might be regional. So far I've only been running TT93's but up here in WI they won't overheat even if run at very low PSI. I might try the PMT's next year. Maybe I'll go tall in the rear but it's the tight chicanes that the bike seems so flickable as it is that I may end up on my ***.
Yes, the overheating of the smaller & lighter 120/70 size was due to severe test conditions(95F temps & 30+ lap stints) which we have experienced in previous 24 hour races. It proved the 120/80-12 size was a more durable tire than the 120/70 over long distances. And they weigh about a pound less(and are half the cost) than the 120/80 TT93 rear, so it was no contest. We have run the TT93s for years, but the newer tires are just better, in our experience.

If I can ever get my "stuff" together, I'm going to try the Kenda tires in stock size. Have the TT93 on my KAYO and they seem to stick like crazy. But the PMY slicks and rains might be a nice thing to have since we can't get the TT rains over here (I forget the model number).
The TT93s and the KD1s are both "soft" compound tires and we have run them each for 12+ hours at 16 PSI and they both performed well up to the limit. The biggest difference is the Kendas are lighter, available in 6 sizes and are much cheaper. We could afford to buy several of each size and test them back to back over the summer until we were confident they would survive the race. In moderate temps the 120/70 will warm up quickly and should not overheat for many laps. It is also much lighter than any 120/80 rear tire. At $50 each, why wouldn't you try one?
 

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Yes, the overheating of the smaller & lighter 120/70 size was due to severe test conditions(95F temps & 30+ lap stints) which we have experienced in previous 24 hour races. It proved the 120/80-12 size was a more durable tire than the 120/70 over long distances. And they weigh about a pound less(and are half the cost) than the 120/80 TT93 rear, so it was no contest. We have run the TT93s for years, but the newer tires are just better, in our experience.



The TT93s and the KD1s are both "soft" compound tires and we have run them each for 12+ hours at 16 PSI and they both performed well up to the limit. The biggest difference is the Kendas are lighter, available in 6 sizes and are much cheaper. We could afford to buy several of each size and test them back to back over the summer until we were confident they would survive the race. In moderate temps the 120/70 will warm up quickly and should not overheat for many laps. It is also much lighter than any 120/80 rear tire. At $50 each, why wouldn't you try one?
I am not a racer, but am very interested in replacing the OEM IRC tires with tires that are both stickier and lighter in weight, while still being, at least technically, street legal. I never ride in rain unless i get caught by surprise. I value "nimbleness" in my motorcycles, and for me heavy tires make a bike feel like it is "wearing cement overshoes". What are my tire choices?

Jim G
 

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I am not a racer, but am very interested in replacing the OEM IRC tires with tires that are both stickier and lighter in weight, while still being, at least technically, street legal. I never ride in rain unless i get caught by surprise. I value "nimbleness" in my motorcycles, and for me heavy tires make a bike feel like it is "wearing cement overshoes". What are my tire choices?
Jim G
The Kendas are DOT rated, lighter & stickier than stock and available in the OEM sizes for under $50 each. Can't do better than that. (And I'm a paying customer, too).

If you look around, the Kendas are $35 each or at least were when I bought mine.

You were running them at 16psi? Seems really low to me and I assume that is a cold pressure. My KAYO has really slow/heavy steering and adding a few psi helped a little with the TT93.
Yes, 16 PSI cold, which ends up about 20-22 hot at our tracks in the warmer weather. Kenda makes a 110/70-12 Front which might change your Kayo's geometry, but I haven't tried one yet. Maybe someone can chime in about it?
 
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