990 Desert Ride: Wide vs Narrow rims (140 vs 150)

Discussion in 'Dakar champion (950/990)' started by Dr LC8, Feb 4, 2020.

  1. Dr LC8

    Dr LC8 ...soon or later

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    Asking for opinion:

    I have been riding around my 950/990 for ages. For hardcore off road I use a set of excel rims 2.5x18 and 1.85x21. So I did in my previous desert trips.
    However most recently I noted an increased overall stability with original size rims when going or hard compound terrain.
    I am embarking in a 10 days Saharan (Algeria) trips where the ground will be a mix of sand and hard compound (old Dakar style).
    I am undecided between 2.5 on 140/80 or 4.25 on 150/70 (rear will run at low pressure 1.2 bar).

    Fire off...
    #1
  2. rinho

    rinho Rinho Féroce

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    Tire can swing
    [​IMG]
    The wider the rim is/Higher the tire is the lower the pressure is, all 3 combined, the lesser stability you'll get.

    The wider the rim is / the lower the pressure is, the more wider contact (grip) on the ground.

    The narrower the rim is the more protected it is.

    Your choice
    #2
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  3. Dr LC8

    Dr LC8 ...soon or later

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    Thanks. In your opinion to ride the 990 in the desert is it better a wide or a narrow tire/rim?
    I was also under the impression (reading and reading published infos) that when you deflate a tire to increase traction (as an example on sand) the tyre increase its length rather than with. And it is the longer print that helps traction rather than the with...

    Cheers

    Nic
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  4. rinho

    rinho Rinho Féroce

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    I'm so experimented in the sand but I guess the LC8 is heavy enough to not make a big difference, I'd go with the more protected rims.
    IMO withd is more impacted than lenght.
    #4
  5. bobone

    bobone Been here awhile

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    you are going solo or with desartica? i'd love to hear your travel report.

    i am a total noob in the sand (just went once in tunisia) but i had 140 on narrow rims, and a friend of mine had 150 on large rims.

    the tyres were different, but the feeling was that his tyre digged less and was more floaty, but mine was a bit more stable and less wallowy.

    but again, different tyres, different setups, etc...
    #5
  6. Dr LC8

    Dr LC8 ...soon or later

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    A group of 6/7 bikes with two support 4x4s.

    I might go with bigger tyres...
    #6
  7. bobone

    bobone Been here awhile

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    when are you going? interested in having me caming along? :D
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  8. Rharr

    Rharr Been here awhile

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    I am very happy with a 1.6 front and a 3.5 rear. I run a 80/100 front tire and a 80/140 rear. I have been using the golden tire gt723 rear and it works great and a tkc 80 front is ok.
    I have now switched to a gt773 fatty front 90/100 and am yet to try it off road, little concerned it's to big.

    in general i found the narrower rims and tires worked better, made the bike more agile and able to dig down a little to find firm soil. I ride mostly desert here in AZ which i assume will be similar to saharan desert. the bike feel much better going though deep sand washes (dry river beds with sugar sand in spots and loose gravel sand mixes in others). the narrow front was the best as it now feels more planted and less float dig float dig with on and off gas which causes chaos if you are trying to keep up speed and stay in the groove. i rather have the front dig a little and a feel predicable then float and plow.

    best advice though with these big bikes is ride angry, keep on the gas and modulate smoothly, no hard panic gas chops if you get scared and rear steer and steer with your weight. That's what gets me through the loose stuff.
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  9. Dr LC8

    Dr LC8 ...soon or later

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    Mandami un messaggio privato
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  10. Dr LC8

    Dr LC8 ...soon or later

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    Thanks for this.
    I used the narrow rims and tyres in my two previous trip in the Sahara with the 990. They worked well. I was just intrigued by trying a wider tyre. There is also another big advantage in the narrow combo: you save around 4kg!
    #10
  11. ferdinotch

    ferdinotch Adventurer

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    Wow, 4kg total ? that's a big improvement on rotating masses and unsprunged weight !!
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  12. albani

    albani Been here awhile

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    I run dual wheelsets on mine.
    1.6x21 a60 up front and 3.5x18 (140 tire)for dirt
    1.8x21 and 4.00x18 (150 tire) for dualsport/street.

    The 1.8 and 3.5 are superlaced on sunrim hoops. I do notice a difference in handling between the two wheelsets, especially the fronts. (I've swapped the front tires around to see which would end up where). There's a weight difference between the two sets.
    #12
  13. Rharr

    Rharr Been here awhile

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    Interesting, what are your observations of handling between the the 1.6 and the 1.8? I have my thoughts, curious of yours. I have and run your dirt setup 100%.

    What front tire sizes do you run?
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  14. albani

    albani Been here awhile

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    90/90-21 on both.
    1.8 seems to be more eager to lean into a corner with a dualsport tire. I wasn't a fan of the 1.8 on a knobby. It could be attributed of the width of the wheel influencing the curvature of the tire's cross section and or the ratio between the front and rear's contact patch with respect to rim width. ie: 1.8/4.0 and 1.8/3.5 vs 1.6/4.0 vs 1.6/3.5. I ran the 1.6/4.0 as my set for the last ~25k miles. Which meant swapping tires anytime I wanted to play in the dirt. Found the 1.8/3.5 at effectively scrap price given they're well seasoned and needed a full go through.
    #14
  15. Off Road Ryder

    Off Road Ryder Long timer

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    I ride and race my 990s with both stock width wheels and a set of SE wheels. I really cant tell much of a difference, other than traction is quite a bit better in the loose stuff with the wider ADV rear wheel. It really shows while climbing steep loose hills.
    I prefer the wider wheel and fat tire in the front regardless of terrain etc. The only reason I have different sets of wheels is for races when I need another set of mounted tires ready to go.
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  16. Johnf3

    Johnf3 Long timer

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    I also prefer the wider wheelset off road. I think there is a noticeable difference in traction and the wider front is more stable and grabs more traction. The looser the conditions the bigger the advantage. Sand is far better on the wider wheels. I also agree that the performance difference is easier to notice on the front.

    The only advantage I see to the narrower rims are durability, and maybe a wider tire choice, but there are only a few tires that work and somewhat hold up on these bikes for true off road conditions anyway and we all know what works after 15 years now. Ha.
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  17. Dr LC8

    Dr LC8 ...soon or later

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    Having tried both several sets several times I think the standard set with a proper off road tyres (TKC, Motoz Rallyz, Golden Tyre, Mitas E9) is better on hard ground. In mud and sand probably the narrow set is more stable and has better grip.
    When you it the road the standard set is way way better
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  18. Off Road Ryder

    Off Road Ryder Long timer

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    Sorry mate! You lost me at TKC :)
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  19. chevtech

    chevtech Long timer

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    I like a wider front tire in the loose stuff ESPECIALLY if it's bottomless. Riding in the Arizona desert near Parker, and just bumped up to a tire that measures 97mm wide inflated to 27 PSI (Tractionator Desert H/T) compared to my last tire being 90mm wide mounted. A little more float up front has done wonders for keeping the tire on top and agility seems to be largely improved when you have to jump out of ruts.

    Hell, I wish they had an even wider front...maybe 103mm or so inflated,

    My .02



    :beer
    #19
  20. chevtech

    chevtech Long timer

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    The narrower your front tire, the higher your "Planing Speed" in loose stuff. Just like a boat, you have to go fast enough to keep our 700lb steed and rider combo from sinking as you go slower. If it's bottomless you have to haul ass with narrow tires to maintain your plane, and control.

    How fast are you?!?


    :hmmmmm:hmmmmm

    Have fun!


    :freaky
    #20
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