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Suspension Set-Up Guide

Enduro Suspension Set-Up Guide

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INSTANT FACTORY SET-UP FOR THE AMATEUR RIDER!

Proper bike set-up will transform your ride. You don’t need any fancy parts and very little technical knowledge. Just apply a little time and patience and work through a simple schedule of adjustments and you can create the most amazing improvements. Honestly, the difference can be mind-blowing… First published in RUST Magazine Issue 5

If you’ve never done this before, then you absolutely must try this, it can transform your riding experience. In just one day, no money down (or maybe just a little), you can change your bike into what will probably be 75% of what a full-factory bike is. It’s so simple it’s ridiculous, and once you’ve done it you’ll kick yourself that you’ve never done it before.

To show you how simple this process is, we’ve done it ourselves. We took a bog standard 2015 KTM 250EXC and a very docile Vet rider (6’0”/1.82m, 14st/89kg) to a standard issue enduro test track and within five hours we had the bike completely dialed, with a set-up (and options) that would last the season – in fact for as long as the rider hypothetically kept the bike.

So here’s our step-by-step guide to factory-standard bike set-up (for dummies).

STAGE ONE: FIT THE BIKE TO YOU

First mission, very simply, is to adjust the bike to fit your physique. Think about it, if you go into a bicycle shop, what do you see? Bikes of all sizes, to suit riders of all heights and weights. The logic is basic: taller people buy bikes with bigger frames. Serious shops even physically measure a rider up for an exact match. You go into a dirt bike shop and sure there are all different engine capacities of dirt bike, but the frame size is virtually identical on all. So what we’re doing here is properly adjusting the bike to best match you.

1: SET THE SAG

We need to start with setting the sag on the shock, which seems a curious place to start, but you’ll soon see why. And this you should do before you go out to ride – do it in the workshop.

Now know this – when an owner’s manual tells you to check the sag with the rider in full kit you MUST do this. Our test monkey (ape!) here is 89kg in his day clothes, in full enduro kit (that’s helmet, goggles and gloves included) he’s a whopping 97kg – that’s 8kg more, a gain of 10%. So wear your kit or your suspension set-up will not be accurate.

Also, don’t take it for granted that if you set the sag last month that it’s still correct today. This bike had just come back from a professional bike test, yet when we checked the settings it had a static sag of 41mm (KTM’s recommendation is 33-35mm). Put 97-kilos of rider in the saddle and rider sag measured 126mm, when target is 105-115mm. That’s way out.

For data collection purposes we test rode the bike in that state and have to say it felt just fine. Without any comparison to work from the rider was reveling in the liveliness and sweet sure-footedness of the 250cc two-stroke. It’s a joy to ride. He could have carried on all day quite blissfully unaware he could have a ride experience that would be so much better, still!

Knowing the sag was wrong we upped the preload on the shock to put the sag back within the right parameters. Winding on the preload is a doddle and inside of 30-seconds we’d re-established 34mm of static sag. However with our test dummy back in the saddle we had a rider sag figure of 119mm. That’s outside of the recommendation by just 4mm – worth worrying about? Honestly, what’s 4mm? So we test rode the bike again and frankly could barely tell the difference – and the rider was still more than happy.

2: CHANGE THE SHOCK SPRING

So, we have established that with a heavier-than-standard rider – despite having the correct static sag – we can’t get within the correct range for rider sag. What we need to do is fit a ‘heavier’ spring. Fortunately KTM have this situation covered. Check out the owner’s manual and you’ll find a table of riders’ weights and the correct shock spring to match.

The standard spring in the 250EXC is 69N/mm, but this is for a 75-85kg rider. For our 97kg rider we need a recommended 72N/mm spring. Cost from KTM is modest, about £80. If you’ve got the tools you can fit this at home but if not any bike shop should be able to do this in no more than 15 minutes. With the shock still located in the frame it takes barely 5-minutes more – so simple is PDS. With the correct spring weight now fitted we measured again and with a static sag of 34mm we got a rider sag of 110mm – bang centre in the range.

Test riding this, the difference was a night-and-day improvement. The rear of the bike felt to ride two-inches higher. And with the rear now riding higher there was less distance for the rider to transition from standing to seated. The bike turned better and landing off jumps it didn’t crash through its stroke so much. Accelerating there was less squat. With the correct spring rate the shock was operating in the correct part of the stroke for all occasions and this dramatically improved the performance. We’d spent £80, but it felt like we’d fitted a £1000 unit!

3: CHANGE THE FORK SPRINGS

Now we don’t take sag measurements on the forks, even though its possible. But fortunately the KTM manual gives us recommendations and again for a heavier rider you do need to fit heavier springs, this time we were upsizing from 4.2N/mm to 4.4Nm/mm springs. And for a pair of springs we’re again talking modest money, around £80 – plus fitting.

Testing this it was immediately apparent that we’d rebalanced the bike. The shock spring alone had made a vast improvement and while our rider liked the way the bike turned so sharply as a result (the back riding higher, the front lower), on balance having a matched set-up in the forks meant the bike was now better balanced in all aspects, maybe not turning quite so sharply, but with the upside of doing everything else better. The bike felt taller and bouncing over jumps and tracking through acceleration and braking bumps everything felt so much more composed – it was massively confidence inspiring.

4: SET THE HANDLEBARS

The 250EXC has two mounting positions for the handlebar clamps, and the clamps can be rotated too to offer four possible positions with in-all 22mm of front-to-back adjustment. Here, to match our 6’0” rider we went for the forward bolting position, with the clamps rotated to give max-forward too. And what an improvement that was. For barely an inch gain there was so much more feeling of space with an added bonus our rider could now get further forward when cornering, improving the grip of the front tyre. There’ll be knock-on benefits too, like less likelihood of arm pump or back strain as the rider can adopt a more natural stance.

And we went one step further, adding KTM’s higher clamps, adding about 10-15mm to the bar height. Now if we were riding rally, or say the Welsh Two Day we’d definitely adopt this set-up, but for short-course enduro – probably not. For short course racing the improved connection with the front end with the lower bar mount outweighs any advantage you’d gain from a more comfortable standing attack position with the higher clamps.

5: NEW SEAT?

We’ve long been fans of the adjustable seats found on adventure bikes like BMW’s R1200GSs as they can really make a difference for taller riders. Unfortunately motocross and enduro bike seats aren’t adjustable, so its been a case of making do.

Now, to be fair, having set the correct suspension spring weights for our rider the feedback was the seat already felt higher – because the rear wasn’t sagging under his weight so much. But having KTM’s next highest seat option ready to try – and if you look at the images you’ll see it doesn’t look much higher, if anything just flatter – we weren’t going to skip on the opportunity.

And what a difference! Our test dummy was bowled over. The transition from seated to standing was now so much less. This is a massive gain for it means the rider is spending much less energy on raising and lowering his torso for each corner. And being a flatter seat its actually helping him put his weight in the right place. Being tall and heavy, when riding with the standard seat and standard suspension the back of the bike was riding low and the curve of the seat meant his bum was also inching backwards, making keeping his weight over the front a real chore – and creating a real stress for the forearms (so inducing arm pump). The higher seat is instead ‘right there’ and its naturally keeping the rider in the right place: close to the front of the bike. Our rider needed to recalibrate the distance his leg had to extend to reach the ground in slow or bermed corners – a few times it just seemed to be dangling – but that’s easy to do.

6: THAT’S IT

And so our rider is now properly fitted to the bike. With the correct springs in the suspension it now operates exactly as the designers intended, it’s not running low with the suspension continually in the wrong part of its stroke. The rider also now has a comfortable cockpit to stand and sit in and with that space and the correct relativities between his hands, feet and bum he’s not going to tire anywhere near as quickly as he had when neither the positions of the handlebars or seated fitted him. Dynamically he is now able to operate the bike exactly as intended, no compromises.

 

STAGE TWO: OPTIMISING THE BIKE TO THE TERRAIN

Having got the bike to match the rider, we can now look at matching the two of them to the conditions. Of course terrain and conditions change, venue-to-venue, so we’re looking at how to manage the bike’s adjusters to make the best match each time, just as the pros do. And again, given the owner’s manual, we can do this far more easily than you might have thought.

1: THE POWER VALVE

We’re talking two-strokes here, but that’s quite a chunk of any paddock. The 250EXC we have here comes with three options on the spring that controls the speed the power valve opens.

‘Standard’ is a yellow-painted spring for ‘medium tuning’ and good rideability. You can alternatively opt for a green-painted spring for softer performance and a red-painted spring for a more aggressive performance. Changing the spring takes about three minutes. Just lay the bike on its side, remove the two bolts that hold the cover over the springs, remove the spring set and swap to the spring of choice, then re-assemble. Easy!

First we changed from standard to the red (aggressive) spring and yes, the performance was noticeably more peaky, the engine feeling that much more willing to rev, like a keen over-sized 125! It was actually – on our test track – really agreeable, it made going faster that much easier and for riding the likes of deep sand you’d pick this.

Placing the green spring in we found a much mellower power delivery as you might want for riding in tight technical going, like thick forest or extreme. To ride fast it took a lot more effort, needing a bit of clutch slipping to urge the revs up quicker.

The springs make a huge difference then and are well worth having in your spares box, ready to make that on-the-day adjustment to suit that wet, snotty enduro (green) or blisteringly dry deep-sand cross-country (red). Standard is just right for probably 75% of occasions.

2: ECU MAPS

We had fitted to the test bike the optional handlebar switch that allows you to swap between the standard and a soft map that are pre-programmed into the stock ECU. It’s another very useful device and when we combined the soft map with the green spring this made for a super-mellow ride. As a racer you’d want this switch, it will make a difference. In fact it was an education just how far you could vary the engine characteristics, from super-snappy to super-torquey given a so-quick and simple play with the springs and maps.

3: SUSPENSION SETTINGS

Let’s all admit to this: the physics of compression and rebound suspension adjustments confuse us. Even world class racers can easily get confused, that’s why they have suspension specialists working full-time in the top teams. KTM know this, and to their credit in their manuals they offer three homegrown recommendations to achieve ‘comfort’, ‘standard’ and ‘sport’ set-ups. Now these aren’t based on guesswork, these are settings they’ve put a lot of work into deriving and so, honestly, they have to be the go-to solution for 95% of us amateur riders. But using them – do they make a difference? Let’s find out.

To start with, swapping the compression and rebound settings from standard to sport – hand-on-heart – it wasn’t that easy to determine a difference. There’s a reason for this. You see, having tested a fair few works bikes over the years, we’ve found that what works for the world’s fastest riders often works just as well for us regular guys too. There is in effect quite a narrow range in which suspension works optimally, whether at high speed or moderate speed – and so the difference between the standard and sport settings really isn’t so great.

However,stepping down to the ‘comfort’ setting we found a massive difference. And around our test course this felt plain awful! The bike flattening itself off the jumps, riding low in the suspension stroke – honestly, nothing we could like. We think KTM should instead call this their ‘extreme’ setting for if this was to work well anywhere we’d say it was for riding a seriously technical wet forest with lots of roots and rocks, and even then only if the speed was slow.

So its definitely worth working with these settings to see how well they match your riding style and local terrain. You may well come up with intermediate settings, but having these fixed points you can at least venture toward those from solid points of reference.

4: JETTING

Your importer/dealer should have set the jetting to the correct settings for your locality, but you can check this by referencing the matrix of carb settings KTM have in the owner’s manual. The over-riding logic that applies here is to set the jet sizes according to altitude and then either change the needle, or the position of the clip on the needle, according to the temperature.

Jetting has been the traditional route to performance tuning, and if you wanted a zingy lively racer you would jet lean, for a blubbery trialsy type performance you’d go rich. But given the developments in power valve and CDI technology we can argue quite persuasively that this no longer applies. It’s better these days to jet to KTM’s recommendations for altitude and atmospherics then use the map and powervalve springs to arrive at the desired engine characteristics.

 

CONCLUSION: YEAH, IT WORKS!

Our test so very clearly shows the benefits in taking the time to follow these few very simple steps to set-up. After literally years, decades, of riding bikes with suspension that was too light, with a cockpit that didn’t fit, it was a revelation for our test rider as to just how much better you could make a standard bike given just a few basic adjustments.

This is, in fact, exactly the process the pros go through when they get a new bike, and it really isn’t rocket science. Okay, at the end of the day they’ll fit A-kit suspension and they’ll get some trick stuff to pep up their engines, but 75%, maybe more, of making a good bike great is exactly as spelled out here. Do this and you’ll find new love for your bike and for riding. As we said, if you’ve never tried this before, try it now. Happiness awaits.

Go to the issues page where all our previous magazines are listed at www.rustsports.com/issues/

 

OUR GUIDE: Gareth Edmunds, KTM UK

Gareth is a top technician. He’s spent years working on bikes at world championships, first with motocrosser Tommy Searle and then with enduro racer David Knight (winning a world championships together). After that he spent years prepping top race cars in the world of GT, rally and endurance racing. These days, with a young family, he’s working with KTM UK, keeping their test fleet tip-top.

“Riders really shouldn’t be afraid of making adjustments to their bikes, and they should understand that they make a real difference. One size does not fit all!

“Work through the processes set out here, it’s exactly the way I’ve worked with the likes of Tommy and David. Take your time, make one adjustment at a time so you can evaluate the change, take notes, and if you ever get lost with what you’re doing you can always revert back to the standard settings.

“When it comes to fine tuning the suspension, try and think logically. For instance, if you’re going to be riding a sandy enduro – say the Natterjack – think about what will work. Sand bumps – whoops – are typically long and even but you can be travelling quite fast. So I’d look to pull the forks through the clamps, to just one line showing, and add a little preload (half to one turn) to keep them high in the stroke. With the shock I’d typically look for a little more low-speed compression damping – just two or three clicks can make a big difference. If it roughs up, I’d then firm up the high speed compression by a quarter or half turn. Rebound damping I’d slow by two or three clicks. For the sag – set this at the top end of the scale (35mm static / 115mm rider).

“But for a tight Welsh forest enduro you need to go the other way, drop the forks back to the standard setting and on the shock set the sag at the lower end of the scale (33mm static / 105mm rider) which will raise the rear so the bike turns quicker, especially in the tight woods and grassy tests. When there are lots of roots I’d soften the damping and speed up the rebound to absorb those short-sharp shocks. It’s a matter of applying simple logic – and testing the results.”

 

The RUST set-up in a nutshell

Suspension: 97kg rider meant heavier springs required

Standard fork springs are 4.2N/mm, we needed 4.4N/mm

Standard shock spring is 69N/mm, we needed 72N/mm

Standard damping settings worked best for mixed terrain of woods and open field test:

Fork: Preload: 2 turns, compression: 20 clicks, rebound 18 clicks

Shock: Low-speed compression: 20 clicks, high speed compression: 1.5 turns, rebound: 24 clicks

Shock: Static sag: 34mm, rider sag: 110mm

Handlebars: Forward mounting position, clamp rotated to forward bias to suit 1.82m rider

Seat: KTM Powerparts High Seat (+20mm, for riders over 1.80m, part no.77207940400)

Powervalve: Standard spring (yellow)

ECU mapping: KTM Powerpart (handlebar-mounted) ignition curve switch (part 51539974100) set to standard (1)

Jetting: Standard: pilot 38, main 175, needle N27H, clip position 3

Tyres: OEM Maxxis 80/100-21, 140/80-18 set at 13psi

Read full article in RUST – Issue 5

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