Trouty

My son has a Mongoose McCan and is well pleased with it. Except as he is only 10 he seems to have a lot of trouble getting up to speed quickly ?
I think the standard gearing is 38 Front and Odyssey 13t Rear Cassette Cog.
He has ridden his mates Haro Mirra 540 which i think has a 39 T Front ? He found this easier but could possibly go a bit more ?
What do you think would be the best combination and best way for me to sort this for him ?

His mate beats him in a drag race as hes flying out the blocks. just want a happy compromise really but need your advice guys ... please.

BMXTRIX

36/13 or 37/13 is pretty close to pro standard. Most pros run about 44 or 45/16 gearing standard (smaller these days). The 38 up front to a 13 will definitely make it more difficult for him to get up to speed, but with enough strength in his legs should allow him to reach a higher top-end speed than his friends who are likely running 39/14 gearing.

Of course, the bike possibly is a little big and weighs a little more than it should for your son which can also slow things down. I'm not sure how big your son is, but the person who designed that bike is in his 20s and is likely over 5'10" tall. This makes the bike very big for a 10 year old. Good for him to ride and get used to, but still big for the next few years.

Not sure what would be better, but he will be ahead of the game for sure if he sticks with the bigger bike now.

Trouty

I sure hope he does stick with it

I also bought him a small set of ramps with a table top. As he only has a short run up (My garden is only 75 ft long). BMXTRIX what would you say would be a good compromise ?

At only 10 years old and around 4 ' 5" inches tall he aint got the legs yet. So im just looking to set the bike up a little better to make it a bit easier for him. he dont really need the top speed thing as tricks amd the ramp will be all he needs for a while.

I thought maybe a 42 Front and keep the 13 back ? would be better than 38/13 ? Would that ajust up ok without messing around with extra links in the chain etc .. ?

cheers for your time ...

CMcMahon

A larger gear in the front will make acceleration harder than a smaller gear. A normal gear (43/44/45-16, 42-15, 39-14, 36-13, 33-12, 30-11, 28-10, 25-9) works fine for just about everything but flatland (and that's more of a personal preference, I think - BMXTrix would know more about that than I). So, if you're looking for faster acceleration, you'd want a smaller gear up front to make the 13, like a 33.

BMXTRIX

Yup, Beerman got it.

You don't want to use his friends bike for comparison. His bike almost DEFINITELY is running 39/14 gearing. Which is very close to 36/13 gearing. But, you may want your son to be able to pick up speed a little quicker, even if he can't go as fast when driving as hard as he can. It'll still be plenty of speed and help him develop his muscles if he goes with 35 or 34 on the front sprocket.

You may have to pull a link out of the chain - get a chain breaker for 5-10 bucks if you don't already own one.

Trouty

DOH ! ....

Thanks for that guys "I meant smaller ... what am i saying bigger" ?

Thats been most helpfull nice work fella's !!!

power

i would leave 36 on the front, look at putting 14 or 15 on the back that should work out better for him. work gearing ratio like this 36 diveded by 13 =2.76 x 20=55.3 so 36x14 =51.4 and 36x15=48.0. look at some bmx race websites you should find gearing chart i think theres one on "ultrabmx" or try "crupi". maybe look at fitting smaller bars junior or expert, bike would feel lot better to him...

Trouty

Thanks Power , Does anybody know any good mail order shops in the UK where i can get a "Cassette 15 tooth rear sprocket" ?

And how easy is it to fit a cassetee type rear ? Do i need any speacial tools for this job ?

BMXTRIX

Most definitely you don't want to switch the back as each tooth you drop from the rear sprocket results in almost a full 3 tooth change to the front sprocket. You go UP in size to make gearing easier, which means you are adding weight to the bike which is also counter-productive.

A big issue may be that the hub you have likely has a one piece sprocket/driver so you would need to get (find) the driver that allows interchangable sprockets on it. The 13 tooth Odyssey driver I am pretty darn sure is one piece. This means you will end up paying 30 bucks (US) or much more likely more in your location, for a rear sprocket change, then you must disassemble the entire rear hub to make the change. A formidible task.

power

i dont know what hub you have on bike some cassette sprockets are easy to change. i would take wheel to a bmx shop tell them what you need. or yea do what bmxtrix says go for 34 or 33 on the front. thought changing rear sprocket would be cheaper than buying front chainwheel?........