I-LikeMatchesDerFun Posted June 11, 2008 Report Share Posted June 11, 2008 (edited) Hi, I am looking to get a new chainring. I'm looking a setting up a better gear ratio(currently 24:16). The crank set I am using is the Onza T-Bird cranks with 24t chainring. I have a 16t cog on the back. I was wondering which chainrings will fit my current cranks? I'm looking to get something like an 18t or 19t chainring. Any help/advice you could give me would be greatly appreciated. Thanks in advance, Steve Edited June 12, 2008 by I-LikeMatchesDerFun Quote Link to comment Share on other sites More sharing options...
walker Posted June 11, 2008 Report Share Posted June 11, 2008 (edited) no, basically if you want a smaller front cog then ur gonna have to buy new cranks and go the screw on way. Cleanbikes do a pair of monty 205pr cranks for £34, you'll also need to take off the freewheel on the rear wheel, this can be put on the front, then u'll need a 12 or 13 toothed screw on cog at the back. Andrew Edit: just realised onza do 20T and 22T chainrings that will fit, they should be fine to lower the ratio a bit Edited June 11, 2008 by walker Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 11, 2008 Report Share Posted June 11, 2008 (edited) As far as I know a 20T is the smallest you'll fit onto that style of crank (I'm assuming the mounting bolts are spaced at the standard diameter for 5 bolt cranks). Unless you fit a smaller bashguard as well you'll get no increase in ground clearance either. If you stay with the 24T front ring around a 20T rear freewheel should do the job depending what ratio you like... If you go for a 20T chainring something around a 16T freewheel should be about right... Edited June 11, 2008 by psycholist Quote Link to comment Share on other sites More sharing options...
I-LikeMatchesDerFun Posted June 11, 2008 Author Report Share Posted June 11, 2008 (edited) As far as I know a 20T is the smallest you'll fit onto that style of crank (I'm assuming the mounting bolts are spaced at the standard diameter for 5 bolt cranks). Unless you fit a smaller bashguard as well you'll get no increase in ground clearance either. If you stay with the 24T front ring around a 20T rear freewheel should do the job depending what ratio you like... If you go for a 20T chainring something around a 16T freewheel should be about right... I'm pretty sure they're standard diameter for 5 bolt cranks. Yeah maybe a 20T chainring and 16T rear freewheel might be the way to go. Cheers Cormac, Steve PS would the following be suitable? Link no, basically if you want a smaller front cog then ur gonna have to buy new cranks and go the screw on way. Cleanbikes do a pair of monty 205pr cranks for £34, you'll also need to take off the freewheel on the rear wheel, this can be put on the front, then u'll need a 12 or 13 toothed screw on cog at the back. Andrew Edit: just realised onza do 20T and 22T chainrings that will fit, they should be fine to lower the ratio a bit Thanks andrew! Just came across them myself! Cheers for the advice, Steve Edited June 11, 2008 by I-LikeMatchesDerFun Quote Link to comment Share on other sites More sharing options...
I-LikeMatchesDerFun Posted June 12, 2008 Author Report Share Posted June 12, 2008 Any of the aftermarket chainrings from Tarty won't fit the T-Bird cranks. I'm going to try Supercycles and see if they can help. Cheers for the replies guys. Steve Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 12, 2008 Report Share Posted June 12, 2008 (edited) Not easy to get 5 bolt 20T inner chainrings . Here are a few options though: http://www.chainreactioncycles.com/Models.aspx?ModelID=3321 http://www.chainreactioncycles.com/Models.aspx?ModelID=30 http://www.chainreactioncycles.com/Models.aspx?ModelID=3322 - Last 2 are in stock... Compare prices with 22T chainrings and you'll see they're not cheap - Run these with an 18T freewheel and the gear should be about right (Though my preference is for a 17T with a 22T chainring): http://www.chainreactioncycles.com/Models.aspx?ModelID=9402 http://www.chainreactioncycles.com/Models.aspx?ModelID=371 Edited June 12, 2008 by psycholist Quote Link to comment Share on other sites More sharing options...
I-LikeMatchesDerFun Posted June 12, 2008 Author Report Share Posted June 12, 2008 This what Adam from Tarty Bikes said: Unfortunately the only chainring that will fit on the T-Bird cranks is the standard fit model. This is down to the chainring bolt spacing (it is Standard Drive, not Compact Drive as all out aftermarket chainrings are), and the mating face of the sprocket/spider are offset from the teeth (not a 'standard' setup). So I'm not sure will any of the CRC ones fit. I'll contact them and see. Thanks Cormac. Steve Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 12, 2008 Report Share Posted June 12, 2008 (edited) Measure the bolt circle diameter (BCD) of the cranks if you have them or of the chainring. This can be done by measuring from centre to centre between the first and third bolt holes on the chainring (Longer measurement reduces error over measuring between adjacent holes) and multiply by 1.0515 to get the BCD. If you're measuring adjacent bolt holes multiply that distance by 1.7013 to get the BCD... Rather than guessing where the centre of the holes is while measuring it's easiest to measure from a tangent at the top edge of the first bolt hole to a parallel tangent at the top edge of the bottom hole. If you get 58mm for the BCD you're sorted - all the chainrings I've posted should fit. If not see does it match one of the other standards given here - if it's a 74mm then 24T is as small as you can go: http://www.sheldonbrown.com/harris/chainrings.html Edited June 12, 2008 by psycholist Quote Link to comment Share on other sites More sharing options...
I-LikeMatchesDerFun Posted June 12, 2008 Author Report Share Posted June 12, 2008 Measured 1st hole to third. ~55.5mm. 55.5 X 1.0515 = 58.36mm. I should be in business with one of the ones off CRC so. You're a wealth of information Cormac! Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 12, 2008 Report Share Posted June 12, 2008 I also keep a large chunk of Rogers Profanisaurus in my head for filth purposes... Can anyone guess what a vulvo is? ... Quote Link to comment Share on other sites More sharing options...
I-LikeMatchesDerFun Posted June 12, 2008 Author Report Share Posted June 12, 2008 (edited) I also keep a large chunk of Rogers Profanisaurus in my head for filth purposes... Can anyone guess what a vulvo is? ... slightly off topic, but would it have anything to do with a ganny? hopefully john will have learned you this word! Edited June 12, 2008 by I-LikeMatchesDerFun Quote Link to comment Share on other sites More sharing options...
NoValidTitle Posted June 12, 2008 Report Share Posted June 12, 2008 (edited) Mods please close. Sorted Steve As a new member who does a ton of searching on the forum might I suggest not editing out your original topic so people who might have a similar problem can better search for the same thing. *edit* I guess a you or a mod put it back. Edited June 12, 2008 by NoValidTitle Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 12, 2008 Report Share Posted June 12, 2008 And to finish - a Vulvo describes a variety of overbuilt female genitalia that would comfortably withstand an offset frontal impact at 30mph, possibly without even setting the airbags off... http://www.viz.co.uk/?domain=viz&page=...rofan_index.php Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.