j0hn Posted March 22, 2013 Share Posted March 22, 2013 I'm thinking of replacing the chain and sprockets on my XT 125 X and contemplating whether to go two teeth up on the rear sprocket. I found out that the R model has exactly the same front sprocket and chain length but 50 teeth instead of 48 for the rear. I know I am to expect a little loss in top end but most of my riding is done in city roads so I could do with more bottom end (acceleration). This probably isn't a fair assessment of speed because the R model has a bigger front wheel but just hoping to get a rough idea of its top speed on the road. Link to comment Share on other sites More sharing options...
dt502001 Posted March 22, 2013 Share Posted March 22, 2013 FYI the speedo is recalibrated for the larger front wheel so top speed is what ever it is reguardless of wheel sizehttp://gearingcommander.com/ fillin the info and you will know the difference. get your race out yet? Link to comment Share on other sites More sharing options...
j0hn Posted March 22, 2013 Author Share Posted March 22, 2013 Yea, that's what I used before but wasn't sure how well that would equate in practice. Theoretically, according to Gearing Commander, I'll be losing around 3mph in 5th gear, which seems fine. Haven't got the race out yet, waiting on a friend to go pick up a heat gun. Link to comment Share on other sites More sharing options...
Grouch Posted March 22, 2013 Share Posted March 22, 2013 The top speed I have had displayed before running out of road is 57 : ( that was on my original and new speedo Link to comment Share on other sites More sharing options...
welshwan Posted March 22, 2013 Share Posted March 22, 2013 on the SuMo wheels i got the clock to say 72 once..... that sure was a big hill! and the 10% or so for the clocks being off slightly Link to comment Share on other sites More sharing options...
BenjiMC Posted March 23, 2013 Share Posted March 23, 2013 i've got up to 74 with a bit of wind but usually hit around 68. 1 Link to comment Share on other sites More sharing options...
j0hn Posted March 23, 2013 Author Share Posted March 23, 2013 68 on a straight? I need to try out the R rear sprocket on my X! Not sure if the actual sprocket would fit though. //Edit R Sprocket and chain kit ordered along with a brand new rear disk brake and brake pads, £150 all together. Link to comment Share on other sites More sharing options...
Grouch Posted March 25, 2013 Share Posted March 25, 2013 Something's wrong with mine only doing 55 ish! Link to comment Share on other sites More sharing options...
j0hn Posted March 25, 2013 Author Share Posted March 25, 2013 Take into account your weight. I guess a part of making your bike go faster is losing some . I bet BenjiMC weighs 60 ±5 KG. Link to comment Share on other sites More sharing options...
Grouch Posted March 25, 2013 Share Posted March 25, 2013 I'm slim lol look at my pic, I weigh 13st. Link to comment Share on other sites More sharing options...
j0hn Posted March 25, 2013 Author Share Posted March 25, 2013 Dude, 13 stone ≈ 82 KG. Not really surprised if you're only getting 55ish. From your picture and what you've said about your build/weight, you're probably a tall guy, so drag will play its part when riding in an upright posture. 1 Link to comment Share on other sites More sharing options...
Grouch Posted March 25, 2013 Share Posted March 25, 2013 I'm six foot and when I'm giving it some I tuck my knees and elbows in. There's something wrong with the bike it should do more. Link to comment Share on other sites More sharing options...
j0hn Posted March 26, 2013 Author Share Posted March 26, 2013 You could try riding like this . But in all seriousness, I think the XT speed correlate with the weight here. BenjiMC - 60kg - 68mph (guessing) Me - 75kg - 60mph (fairly accurate) Grouch - 82kg - 55 mph Not enough data for this graph to be accurate but from what's available, you can see the line of best fit is pretty close to the data points. So, from a statistical point of view, I don't think there is anything wrong with your bike. Link to comment Share on other sites More sharing options...
Grouch Posted March 26, 2013 Share Posted March 26, 2013 Ok I believe you lol Link to comment Share on other sites More sharing options...
bippo Posted March 26, 2013 Share Posted March 26, 2013 The speed of your XT will no longer matter Grouch when you've got your 2T play-thing...! Link to comment Share on other sites More sharing options...
Grouch Posted March 26, 2013 Share Posted March 26, 2013 The speed of your XT will no longer matter Grouch when you've got your 2T play-thing...! I know I just can't decide what to get, want a Mito but if I see a nice TZR or RS I'll get it, depends what's about at the time and how much I think it's worth. Link to comment Share on other sites More sharing options...
BenjiMC Posted April 24, 2013 Share Posted April 24, 2013 i weigh around 65 KG but often have my uni bag with books etc weighing in a fair bit plus panniers with tool kit and spare shoes to wear around teh library, still will hit over 60 easily on the flat. I do find a lot of extra speed when i tuck being 6ft myself but also how much i tuck too can get that little bit extra out. bear in mind i have the R vs the X which has higher top speed anyway. Link to comment Share on other sites More sharing options...
j0hn Posted April 25, 2013 Author Share Posted April 25, 2013 Hah, you see that graph, I was pretty close . Not sure if R has a higher top speed, they are the same engine. Link to comment Share on other sites More sharing options...
Ryan09 Posted April 29, 2013 Share Posted April 29, 2013 You have too much time on your hands j0hn haha Link to comment Share on other sites More sharing options...
Prichard XT Posted April 29, 2013 Share Posted April 29, 2013 I ride the Xt125R and whent down from 14t to 13t on the engine sprocket lost 5 mph off to end but gained bottom end acceleration/torque the only problem in the chain eats in to the two sprocket bolts Link to comment Share on other sites More sharing options...
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