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Offline Bensien

Which rear tyre sizes for off road racing
« on: April 20, 2015, 06:29:58 am »
Iím trying to make sense of the manufacturersí recommendations. The Europeans seem to favour a 140/80 rear, but recommend anything from 120-140. The Yamaha WR450 comes fitted with a 110 and the 250 with a 120, The Honda 450X has a 110 rear tyre and the 250X a 100 or 120, depending on who you chose to believe. There doesnít seem to be any correlation between bike and tyre size.

So my question is, if you could get your tyres for free, what rear size and compound would you choose for trail riding, enduros and rallies?
Why do things that only happen to stupid people always happen to me?
 

Offline Vintage_Mania

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Re: Which rear tyre sizes for off road racing
« Reply #1 on: April 20, 2015, 06:54:12 am »
In SA it is mostly 110/120, the bulk of tyres and threads will be in that size. The 140's are becoming scarce these days, use to be the "in" tyre in the 80's going into the 90's, a lot of the VMX guys still use them in the bigger 2T bikes. I won't fit a 140 on anything smaller than a 450, which these days usually run with 120 as standard. 110 should handle better than a 120 in ruts and hardpack, where 120 will be better for soft sand and muddy conditions being wider. Also keep in mind the sidewall lengths. The side wall indication is a percentage of the width e.g 120/80 has a sidewall that is, in length, 80 percent of the width. And 120/90 is then obviously 90 percent of the width, and a longer sidewall. Here again you will have better luck with the 120/90 running it softer in muddy and rocky terrain, while the 120/80 will be a better bet running it harder on track and hardpack.

As I understand it, not a tyre pro.

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Offline Cracker

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Re: Which rear tyre sizes for off road racing
« Reply #2 on: April 20, 2015, 07:31:17 am »
I currently have a 140 rear on my 450 but that's because that's all that was in stock when I was in the shop - I'd usually  buy a 120.

It is big! Very big! And looks even bigger!  :biggrin:

Unfortunately, I'm not at the skill level to say whether it's great or not but I like it. I'm getting good life outta the knobs and it seems to ride mud and sand better. But I now feel like I'm unsure where the breakaway point is between traction and spinning, maybe I just have to get used to it. It gave me a high-side a while back that was really unexpected.

My next tyre will be a 120 again and will I stick to the scorpion XCs just because that's what I'm used to now. I'm not faster than the bike, so I'd rather have it consistent and I can 'learn' to ride faster.

So my choice is based on my own history, not on what the pros might recommend. If I wasn't racing though, I'd probaly fit a desert front and C02 rear for longevity and puncture resistance.

Not great for enduro but nor is a 450 ................. 
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Offline Bensien

Re: Which rear tyre sizes for off road racing
« Reply #3 on: April 20, 2015, 08:22:50 am »
Iím trying to convince one of the tyre importers to ask the factory for some promotional freebies to give away at races. I want to make sure they will be in sizes that most people would use anyway if they paid for it.

It seems that 120/90 is the most popular rear and 90/90 21 the most popular front, but there's a choice of full enduro tyres in hard, medium and soft compounds, FIM homologated road legal rally tyres, and 60:40 DS knobblies.
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Offline Bill the Bong

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Re: Which rear tyre sizes for off road racing
« Reply #4 on: April 20, 2015, 08:27:12 am »
In the KTM range only the models that come delivered with a road worthy kit tend to have 140 spec'ed.  And I think that's mainly due to there being more real knobblies in 140 that have DOT approval.

I put a left-over 140 from Amageza on my 300 and I could not get it to work at pressures above 0.4 bar.  Quite a lot of 140's have reinforced sidewalls.  Only saw that when I removed the tyre.
 

Offline Bill the Bong

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Re: Which rear tyre sizes for off road racing
« Reply #5 on: April 20, 2015, 08:29:13 am »
Iím trying to convince one of the tyre importers to ask the factory for some promotional freebies to give away at races. I want to make sure they will be in sizes that most people would use anyway if they paid for it.

It seems that 120/90 is the most popular rear and 90/90 21 the most popular front, but there's a choice of full enduro tyres in hard, medium and soft compounds, FIM homologated road legal rally tyres, and 60:40 DS knobblies.


90/90 21 is usually more a dual sport size.  Most of my off-roads like a 80/100 21.
 

Offline Bensien

Re: Which rear tyre sizes for off road racing
« Reply #6 on: April 20, 2015, 07:48:20 pm »
So If I suggest to the importer to ask for some medium compound knobblies in 120/90 18 and 80/100 21, the majority of riders will have a use for them?
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Offline bonova

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Re: Which rear tyre sizes for off road racing
« Reply #7 on: April 20, 2015, 09:20:29 pm »
My personal opinion is that it is very specific to the ride and not the bike. After all the tyre is the thing that gives you traction and stability. That has very little to do with the bike and alot to do with what you are riding in terms of terrain.
I have a 250 2T..... My Tyre choice is a 130 or 140 rear. (EF 07) Soft  compound with soft sidewall. You cannot beat these tyres for traction on knarley rocky climbs. On the fast single track and roads they are not as good and they catch on narrow rutts and obstacles.
The rim on the smaller bikes is narrower.... Hence the "wider" tyre will end up having a deeper profile. This means you can run it softer (or older mousse) without worrying about denting rims. Put a 110 tyre on that same mousse and its profile is very low comparatively
I have ridden the 110 and 120's obviously and they seem to corner better and handle speed better on that specific bike.

On my 450 i run a 140 rear. Its also stiffer sidewall and harder compound to handle the speeds and power of the rallye rides

From what ive seen at the events ive been to.... The guys from JHB favour the 110 tyres. They are batt outa hell fast on the single track but if an ant pisses on a rock they get stuck on it  :biggrin:
The rock rabbits from KZN favour the 130/140's they get passed by the jhb guys on the flats and then moan about bottle necks on the climbs.....sometimes riding over the jhb guys and using their bikes for traction.
The guys from the cape....mmmmm do they even ride offroad bikes without sand scoops?  ;)

 :ricky:

I see you are from JHB. So if i do the math..... Yes 110/120 rear. Meduim compound else there will be moaning about tyre lifespan.  That way youll cater for the majority ;)

« Last Edit: April 20, 2015, 09:24:43 pm by bonova »
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Re: Which rear tyre sizes for off road racing
« Reply #8 on: April 20, 2015, 10:05:16 pm »
I was running a 140 E-07 with an Ultra Heavy Duty tube on the rear on my XR650L. It was OK most of the time but did not handle the sandy whoops at all coming from the pipe bridge at Mfula Store at the south side of the Umgeni. 3 weeks later I changed to a 130 Michelin T63 and replaced the tube with a normal HD item. The bike was totally transformed with the rear suspension working as it should. Sometimes too much unsprung weight is too much. Much better now with the smaller and lighter rear wheel.
 

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Re: Which rear tyre sizes for off road racing
« Reply #9 on: April 21, 2015, 07:49:37 am »
My personal opinion is that it is very specific to the ride and not the bike. After all the tyre is the thing that gives you traction and stability. That has very little to do with the bike and alot to do with what you are riding in terms of terrain.
I have a 250 2T..... My Tyre choice is a 130 or 140 rear. (EF 07) Soft  compound with soft sidewall. You cannot beat these tyres for traction on knarley rocky climbs. On the fast single track and roads they are not as good and they catch on narrow rutts and obstacles.
The rim on the smaller bikes is narrower.... Hence the "wider" tyre will end up having a deeper profile. This means you can run it softer (or older mousse) without worrying about denting rims. Put a 110 tyre on that same mousse and its profile is very low comparatively
I have ridden the 110 and 120's obviously and they seem to corner better and handle speed better on that specific bike.

On my 450 i run a 140 rear. Its also stiffer sidewall and harder compound to handle the speeds and power of the rallye rides

From what ive seen at the events ive been to.... The guys from JHB favour the 110 tyres. They are batt outa hell fast on the single track but if an ant pisses on a rock they get stuck on it  :biggrin:
The rock rabbits from KZN favour the 130/140's they get passed by the jhb guys on the flats and then moan about bottle necks on the climbs.....sometimes riding over the jhb guys and using their bikes for traction.
The guys from the cape....mmmmm do they even ride offroad bikes without sand scoops?  ;)

 :ricky:


I see you are from JHB. So if i do the math..... Yes 110/120 rear. Meduim compound else there will be moaning about tyre lifespan.  That way youll cater for the majority ;)



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Offline Bill the Bong

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Re: Which rear tyre sizes for off road racing
« Reply #10 on: April 21, 2015, 09:52:04 am »
In dry sand, any mid-soft/inter-soft in 120 will work well on a <500cc enduro/off road.  In my experience, in deep, wet sand nothing works, except for the mechanic afterwards  :P