Who's done front sprox mod !

[Aussie Dave]

I knew it.... The local yokel's "are unable to help....."

Every SDR & GT owner in Aus must be wanting to tweak their gear ratios (what,all three of them ).... - I saw the first and only other GT at a fuel station last Sunday.....and the bastard didn't even notice my GT parked nearby....... ...... bloody Euro bike riders......all the same.......

Ok, only enough enthusiasm left in the tank to have one more try before I totally stop spending any more $$ and just ride it as a 5 speeder........ .......I could order the Sitta Alloy ones from the enterprising UK stockist's, but prefer good old steel for our harsh/dusty/high mileage conditions.... ..... reminds me of a mate who raced his modified 900 SS Ducati......he used a 'nylon' rear sprocket - we all thought it would break, but he was doing great wheel stands, and raced for years without failure.

Thinking positive thoughts.....Oooommmmm......

[AllanP]

Some great info in this thread. I went 2 teeth larger on my 990SD and appreciated the difference and I think I'll be going for a 39 or 40 on the SD-GT. I'd be interested to know much do the different sprockets change the length of the wheel base?

[DaveNZ]

Some great info in this thread. I went 2 teeth larger on my 990SD and appreciated the difference and I think I'll be going for a 39 or 40 on the SD-GT. I'd be interested to know much do the different sprockets change the length of the wheel base?

I put a 40 tooth on Allan, id say it shortened the wheel base maybe 10 mm max, i doubt id notice any difference in handling, may be steer a little quicker, but who would notice. I'm happy with the change to 40 tooth, i don't think theres much to gain by going 39, but it may suit some guys who are want a small change.

[MR C]

Some great info in this thread. I went 2 teeth larger on my 990SD and appreciated the difference and I think I'll be going for a 39 or 40 on the SD-GT. I'd be interested to know much do the different sprockets change the length of the wheel base?

i don't think theres much to gain by going 39, but it may suit some guys who are want a small change.

You need to try both, there's still a noticeable difference with a 39t, wheelbase is marginal, whereas the 40t takes the wheel fully home and will slightly alter the wheelbase but I never really noticed any difference whilst riding, also I'm not sure if the the eccentric adjuster will alter the height slightly !

I like the 40t and it's great, instant drive, it feels ballistic and so addictive, the 39t is the great also, you still have the long (ish) gears so you can ride fast twisties in one gear just roll off - roll on without the need to cog up, it retains good mpg (with 40t I noticed a big increase in my fuel bill but that could be down to riding like a cock) and 39t will allow you to sit comfortable on motorways @ 70 mph. However it really only takes 15-20 mins max to swop over so you can have the best of both, I'm off to Spain next week and getting to the ferry is m-way and it's a 3k trip so I've opted for the 39T on return I'll put the 40t on for odd days out.

Also I've done roughly 3700 miles (total mileage is just over 5500 now) with the sitta sprox fitted and there's no wear.

[Aussie Dave]

Yep, I'm attempting to buy both the 39 and the 40.......though for my Aussie 'conditions' (ie speed cameras behind every bush.....and unmarked patrol bikes.......well,..... not all the time ) the 40 will sit nicely with the extra 350 rpms putting the motor into it's smooth sweet spot (4500rpms) for the majority of Aussie road speed limits and traffic flow.

DaveNz and MrC have commented on just how quick the 'quick change' is.....so it's no drama having both available......I was also thinking .... while out riding today.......it will be handy to have the optional sprocket on hand at tyre replacement time......not all brands of bike tyres have the same rolling diameter even though they are all labelled 190/55.......some are bigger eg Bridgestone, others are heaps smaller eg Dunlop, and I think the Michelin PR4 that I am likely to select for the rear is 'not small & not large' for it's sizing. So handy to have the other sprocket on the shelf just in case the choice of new tyre also alters the gearing.

Gawdammit......Esjot just emailed a reply advising me to contact the local agent for their sprockets...... done that already...... that's why I went to Esjot to try to get them.........grumble, mutter,

Gotta go out for a feed soon, so will try yet again.....but it isn't looking good......nothing comes up in my searches........Aussie agents (Metal Gear in Brisbane!....that's my city!)....bike too new for them to bother ordering stock..... might have to go alloy Sitta brand out of good old UK...

[AllanP]

I have to go away for a couple of weeks starting next week but will try to get a 40T ordered before I leave and fit it when I get back. Got 8000km/5000miles on the bike now and its been running well.

[AllanP]

I got back from my trip only to find that SuperSprox had run out of 40T rear sprockets but being bit impatient I decided to try the only alternative they had in stock which was a 39T. Simple arithmetic would tell anyone that such a small change wouldn't make much difference ..........but of course that didn't stop me

So I carefully noted the engine rpm at various speeds with the standard 17/38 on a road I know well where I also know how comfortable the bike is pulling up hills and cruising at different speeds in 5th and 6th. I fitted the 39T and adjusted the chain to give about the same slack and measured the change in wheelbase -10mm.

Today did about 200 miles on the roads mentioned above and can report that if the 1-tooth larger rear sprocket makes any difference at all, its barely perceptible to me, a bit of a waste of time

I may try a 40T in the future which is what I really wanted, but that will have to wait till after my summer trip to Oregon.

[DaveNZ]

^^^Jeeeeze Allan, 40 is the magic number, forget 39, the smile dial starts at 40, hasn't all those past years taught you to be patient.

[MR C]

Very strange because I can tell a difference especially when cruising, no more lugging with the 39 and have done 6k with this size sprox, recently I've been swooping back n fourth with the 40 and whilst the 40 does make a huge difference not only to pickup but the quickshifter seems seamless.

[AllanP]

Half of the problem with the SD-GT is that its so easy to change the rear sprocket, and its interesting to experiment so I couldn't wait

DaveNZ: The magic 40T will go on in September when I get back from my road trip although by that time I might have 12k-15k kilometers on the bike and will change both sprockets and the chain. The old sprockets could still have life left in them but if the 40T gearing seems to be where I want it, I'll also fit a new longer chain so I can get the wheelbase back. For the roads I have here I don't need a quicker turn-in and would prefer more stability for fast bumpy bends accelerating when the front wheel is only nominally on the road.

Mr. C: I was exaggerating a bit when I said the difference with the 39T was "barley perceptible". I can definitely feel it and will keep the 39T on until I get the 40T and may swap them back and forth depending on where I'm riding. We have 120-135 km/h speed limits in a lot of the South West of the USA and the 39T would be a good choice on a longer road trip out there. One thing I look at is optimizing fuel consumption because of the huge distance between fuel stations and I think the 39T might be better than the 38T for that. As I'm sure you would agree that low revs if the engine is not happy don't always make for the best fuel consumption.

[MR C]

, I'll also fit a new longer chain so I can get the wheelbase back. For the roads I have here I don't need a quicker turn-in and would prefer more stability for fast bumpy bends accelerating when the front wheel is only nominally on the road.
.

This I totally agree and exactly my thoughts whilst riding, running the 40t I've noticed its reacts very quick to turn in has lost some stability, whereas before it felt planted and now it's like a scalded cat !! I personal think 40t and stock wheelbase would be absolutely perfect transition.

I've not measure the change in wheelbase but do you think it needs one and half links added ?

[AllanP]

Even with the 38T the bike acceleration is limited in the first 3 gears by wheelies not thrust and I don't think lowering the gearing buys you anything. With my skinny ass on the bike 4th is not too stable either and hitting a big bump causes the front to go light the practical difference for me is in 5th and 6th and its fun to play around with the gearing. I just ordered my first tire changing equipment and I think I'll be swapping them out more often too.

[SuperDukeGT]

I've seen a lot of queries from guys on this site wanting to know where to get sprockets (and chains) from in terms of changing the gear ratio. I've spent quite a lot of time looking and the place that I've had the best luck with is SuperSprox https://www.supersproxusa.com/ where you can find aluminum, steel or a combination of both and high quality chains. For myself, I have just ordered a 41 tooth rear sprocket and new 525 chain from them. They were quite helpful. Good luck.

[Aussie Dave]

Thanks SDGT.......now I know why you wrote 'good luck'

I stumbled around the website (USA & EU) but could only find the stock 38T....... my searches didn't work (error) and the site didn't have the usual brand & bike style index (only in the "buy now" section - which led me to the stock sprox's.... ).

Maybe it was an off day.....for me and for the site....

The 41 tooth sprocket is unusual .......it might be about the same as going for 1 tooth less on the front or maybe it will shorten the gap to 6th without making 1st too short ...let us know how it works.. .

[MR C]

@SDGT are you keeping stock wheelbase, if so how many links is the chain .

[SuperDukeGT]

The contact information I have for SuperSprox is, as follows:

Craig Nadeau
Sales Account Manager

Toll Free (800) 328-5454, Ext. 536
Direct (763) 255-2536
cnadeau@arrowheadep.com

Dave was very helpful and I'm not at all certain as to why you are having difficulty with the website as I just checked and it is working just fine.

Yes, I have purchased a new GB525GXW, 120 link chain and a new 17 tooth front sprocket with the new 41 tooth rear sprocket. Changing both sprockets and the chain is recommended to ensure even wear, etc. I am not in favour of changing the front sprocket down to a 16 tooth as it is harder on chain wear.

[Aussie Dave]

Cheers SuperdukeGT........just tried the link again this afternoon and hey presto......it worked

They are still showing the 40T black (steel) as n/a, so I'll be hanging on some feedback about your 41T.

I'd probably bee happy with the 39T as it just takes some of the load off the motor at strictly legal speeds (like when you have an unmarked BMW R12RT on your tail......you know...white helmet, video cam on LHS, and blue & red christmas lights on the handlebars and a big fat radar scanner pointing forwards.......just riding with me for company...eh? ). Thank Fek for the cruise control button

Anyway, I'll try again after xmas......maybe they'll have stock of the 40T..

Ps It's quite surprising how after 10,000kms (6000mls) the gearing doesn't seem to be as much of an issue, I'd say I've adapted to the bike, but also, as everything has worn in (less friction resistance etc) the gearing is ok - the only issue is the huge gap from 5th to 6th (basically an Auto-strada overdrive) - so KTM, for 2018, make 6th a closer ratio to 5th and that'll be about perfect for the next gen Gt owners