Hi there, i have a DMR drone dirt/jump bike and the bottom bracket is loose i think it needs new bearings does anybody no how i can find out what size i have to order for this to be fixed, also another thing the back sprocket (the chain ring on the back wheel) is slipping and not caching to ride how could i fix this problem thanks for your help!!...

Regarding the bottom bracket, a picture would be helpful to allow us to determine what it's got.

As for the sprocket (not the chainwheel, that term only refers to front sprockets), there are a number of issues that could be taking place. Firstly, the pawls in the freewheel mechanism could be gummed up with old grease. This isn't uncommon, and can be fixed by flushing or cleaning out the freewheel mechanism.

Secondly, the pawls or ratchet in the freewheel mechanism could be worn out, or the pawl springs could have failed. Repairing this will require new parts, and depending on the model of hub, replacement parts may or may not be available.

A third possibility is that the sprocket is worn and that the chain is skipping on it as a result, which is more likely to be an issue if you've recently replaced the chain with a new one. Again, if the sprocket is worn, it'll need replacing, which may mean you need a new sprocket, a new freewheel or possibly an entire replacement driver assembly depending on the type of hub you have. What model rear hub is it?

You mean one of these ... .https://www.sunsetmtb.co.uk/shop/inde...product_id=983

Er, take it apart and look?.. I suspect the rear freewheel has gone out. might need it rebuilt, or replaced

I'd enlist the bike shop's help, since I cannot see anything you are talking about,
and I have no Idea about what tools you have available ..
if its a screw on Freewheel you need the freewhweel removal tool specific to the brand of Freewheel they installed.

......find some help. There's no way anyone can do this for you over the internet given your level of mechanical sophistication.

i could send you pictures tomorrow but every thing is there, and could you explain abit more to me about how to take off the flywheel ECT thaknks...

do you no what size bearings i would need for the bb

yes fietsbob it is that bike

The questions you are asking indicate you are totally out of your depth with bike maintenance, as 3alarmer notes, there is only a limited amount of support that can be given remotely via the internet, and the recipient has to know how to put it into practice.

Suggest you find a good LBS, and they should be able to resolve the issues you are having with your bike. Guessing you are in the UK, as DMR are a UK brand, and primarily sold here, you would want to find one with an Upgrade account, so they can order any spares unique to the bike.

Freewheel not flywheel, and I can't begin to explain it as there are at least four possible ways you might have to do it depending on the type and model of the hub.

As for the BB, there's a multitude of different BB shells your frame could have (BMX Mid, BMX Spanish, Ashtabula/BMX USA, threaded/BMX euro and probably more I can't think of) with various different degrees of replaceability. For instance, if you have a BMX Mid BB, with BMX-type cranks, all you need to replace is the bearings. If you have a threaded BB shell and a cartridge BB, you'll have to replace the spindle as well as the bearings. There are one hell of a lot of potential combinations.

Where in the UK are you located?

im from wales, and okay would it say on the bb what size i need or what size bb, if this makes sence and there is alot off diffrent ones, if i take a picture of it apart and send it to you tomorrow would you beable to tell me which one i need thanks...

You really need to go to a LBS for this, as previously; from the infomation you have supplied, you don't yet know the way to describe key bike components, if you go to a LBS, they can ID and describe them so you will know for the future.

You really need to get someone to look at this hands on, if you take it apart, you may loose parts. Is there any reason why you can not go to say Sunset, they are open 10-4 tomorrow?

No, I'm 1/3 of the globe away, to the west..

Its in front of you take the bearings out and measure them, Like I said,
if you cannot, then you need to Hire the help, of a Bike Shop.

It might say, if you're lucky. The picture would be helpful. A picture of the rear hub would also be helpful in working out how much of it you might need to replace.

The DMR Drone (Mks. II, III & IV) takes it's own kind of funky bottom bracket - it's 68mm, same as a lot of bikes (ISIS standard), but it's own weird-length spindle AFAICT:



(From ChainReaction - £17.99)

The Mk. 1 takes another, similar type:



You need one of these to remove/install them:



As far as the freewheel at the back (single cog BMX-style), you're best off posting a picture of it, as they can use different types.