Re: Suspension Upgrades for the Royal Enfield Interceptor 650 & Continental GT 650 Twins surjaonwheelz, you brought up some really good questions. I am listing my hands on observations with the adjustable rear suspension on my Triumph and online learnings (Dave Moss Youtube videos are an excellent source). I dont have adjustable suspension for the front on either of my bikes. I had planned to get preload adjusters for the front of the Continental GT 535 but with the change in the fork oil, it feels good now. The rear gets infinite preload adjustment (unlike the 650 twins which get 6 step preload). I might go for an inexpensive Indian made front preload adjsuter, just to experiment with it down the road.
For my Street Triple 675, the bike feels beautifully balanced, so I dont need to preload adjusters at the front. The rear is the Ohlins TTX with preload, compression and rebound adjustment. Hence I cant really speak with practical experience for the front suspension there either. With that elaborate disclaimer, let me share a few points, hopefully we can learn from our experiences.
- This might be an oversimplification, but the primary factors that we consider for a motorcycle suspension are sag, preload, compression and rebound. The factors affecting this are the fork oil, fork springs and if available, preload adjustment.
- Motorcycle suspensions are setup for purpose based on the average rider profile and usage. So one size may not fit all. Specific to the front end
- The 650 twins are known to have soft front suspension and many riders I know have experienced some front dive, especially with hard cornering.
- For riders who dont experience this (on account of lighter rider weight, less aggressive riding styles) no change is necessary. Just replaced the fork oil every 3 years or 20K kms (ballpark figures that I am throwing out) and they should be fine.
- If the front end is soft and the rear is firm / perfectly set, this can create a slight imbalance as the front wants to go up and down but the rear is steady.
- For riders who experience front end dive, we can change either the fork oil, fork springs or add preload adjustment.
- Thicker fork oil will reduce the compression and rebound. Its a bit of an inexpensive fix. But without a large enough baseline, its trial and error. For a particular rider weight and riding style, do we upgrade to 5W? 5W light? 7.5W? 10W? For 2 riders with same weight and similar riding styles, one might be OK with 5W but another might prefer 7.5W. Both are correct.
- Fork springs are an expensive fix but when done right, they can be the only change we need. International vendors are offering weight specific springs, and they have the decades of experience to fast track development and get the right springs for each particular rider weight. Indian vendors have only recently started getting into this space but they know our Indian conditions better than most.
- I believe (I might be wrong here), Indian vendors are giving combinations of stiffer springs + thicker fork oil. So that reduces your experimentation and it should work. But without trying it out, its tough to say whether it is the right combination.
- Preload adjustment helps in two ways. One it sets up sag correctly and two, it helps control rebound and damping by making the suspension stiffer or less stiff (see last point in the post).
For a moment, lets take a break from the 650 twins and assume that we are talking about a sports bike with adjustable compression, rebound and preload for the front end. Why do we need preload? Let me try to explain with a crude example. Lets assume a 0 to 100 "hypothetical score" for combined suspension settings, 0 being the softest and wallowiest setting. And 100 is the most hardcore, stiffest setting. Now if there are 10 preload settings, each one goes to 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 on the score. The compression and rebound adjustment will help finetune the score. So if your preload is set at level 3, you are at a score of 30. Then by adjusting the compression and rebound, you can go down to 25 or up to 35. Lets assume that the manufacturer might have set this up for a score of 54, based on average rider profile and usage. But for your usage, you need something more hardcore like 77.
Now if you have full suspension adjustability, you can take it to 80 and fine tune the compression and rebound to get it to 77. You might realize, that is fine for weekend riding but for monday to friday, you need something more comfortable. So then you take preload to 60 and adjust it to take you to 63. All of this works if you have full adjustability.
But in the case of the 650 twins, none of the aftermarket manufacturers are offering sports bike like suspension with compression and rebound adjustability for the front. So you use your preload adjusters, to take it to your comfortable level. So from say 40 (given how soft it is), you can go to 60 or 80, but not 63 and 77 respectively. But without preload adjusters, you are stuck at 40 and have to keep on changing fork oil etc.
- Ive not heard of heavier fork oil resulting in heating and that causing an issue. I need to read up more. Specific to the rear end
- The current 6 step preload adjustable Gabriel shocks seem fine to most riders.
- Ideally, a fully adjustable rear shock is a very nice to have addition. I would focus on fixing the front first.
- On the road, changes to preload make a massive difference. Recently I stiffened the rear on my Triple 675 by changing the preload. Despite changing the compression and damping to the comfortable setting, the whole setup was way too stiff. So I had to undo the preload change, to get back to normalcy. |